Fix TRAP restore PC, but better

core/cpu.c

@@ -91,11 +91,6 @@
 #define CPU_XORBSU   82
 #define CPU_XORNBSU  83
 
-/* Functional operand types */
-#define CPU_LITERAL  0
-#define CPU_MEMORY   1
-#define CPU_REGISTER 2
-
 /* Bit string operations */
 #define CPU_AND_BS  0
 #define CPU_ANDN_BS 1
@@ -1642,6 +1637,7 @@ static void cpuSUBF_S(VB *sim) {
 /* TRAP */
 static void cpuTRAP(VB *sim) {
     sim->cpu.clocks += cpuClocks(15);
+    sim->cpu.pc     += 2;
     cpuThrow(sim, 0xFFA0 + cpuGetImm5U(sim));
 }
 

core/timer.c

@@ -5,6 +5,15 @@
 
 /***************************** Module Functions ******************************/
 
+/* Compute clocks until the next decrement to zero */
+static uint32_t tmrGetUntil(VB *sim) {
+    uint32_t fullTick = sim->tmr.t_clk_sel ? 400 : 2000;
+    uint32_t thisTick = sim->tmr.clocks +
+        (sim->tmr.t_clk_sel ? 0 : 400 * (4 - sim->tmr.tick20));
+    return thisTick + fullTick *
+        (sim->tmr.counter == 0 ? sim->tmr.reload : sim->tmr.counter - 1);
+}
+
 /* Update the counter to a new value */
 static void tmrUpdate(VB *sim, uint16_t value) {
     if (value == 0 && sim->tmr.counter != 0) {
@@ -23,10 +32,6 @@ static void tmrUpdate(VB *sim, uint16_t value) {
 /* Process component */
 static void tmrEmulate(VB *sim, uint32_t clocks) {
 
-    /* Timer is disabled */
-    if (!sim->tmr.t_enb)
-        return;
-
     /* Process all clocks */
     for (;;) {
 
@@ -38,15 +43,22 @@ static void tmrEmulate(VB *sim, uint32_t clocks) {
         }
 
         /* Advance forward the component's number of clocks */
-        clocks         -= sim->tmr.clocks;
-        sim->tmr.until -= sim->tmr.clocks;
-        sim->tmr.clocks = sim->tmr.t_clk_sel ? 400 : 2000;
+        clocks          -= sim->tmr.clocks;
+        sim->tmr.until  -= sim->tmr.clocks;
+        sim->tmr.clocks  = 400;
+        sim->tmr.tick20 += sim->tmr.tick20 == 4 ? -4 : 1;
+
+        /* Do not decrement counter */
+        if (
+            !sim->tmr.t_enb ||
+            (!sim->tmr.t_clk_sel && sim->tmr.tick20 != 0)
+        ) continue;
 
         /* Advance to the next counter value */
         tmrUpdate(sim, sim->tmr.counter == 0 ?
             sim->tmr.reload : sim->tmr.counter - 1);
         if (sim->tmr.counter == 0)
-            sim->tmr.until = sim->tmr.clocks * ((uint32_t)sim->tmr.reload + 1);
+            sim->tmr.until = tmrGetUntil(sim);
     }
 
 }
@@ -71,8 +83,10 @@ static void tmrReset(VB *sim) {
     sim->tmr.z_stat    = 0;
 
     /* Other */
+    sim->tmr.clocks  = 400;
     sim->tmr.counter = 0xFFFF;
     sim->tmr.reload  = 0x0000;
+    sim->tmr.tick20  = 0;
 }
 
 /* Determine how many clocks are guaranteed to process */
@@ -88,14 +102,27 @@ static void tmrWriteControl(VB *sim, uint8_t value) {
     if (
         (value & 0x04) && /* Z-Stat-Clr */
         (
-            sim->tmr.counter != 0 ||
-            !sim->tmr.t_enb
+            !sim->tmr.t_enb ||
+            (
+                sim->tmr.counter != 0 &&
+                !(value & 0x01) /* T-Enb */
+            )
         )
     ) {
         sim->tmr.z_stat = sim->tmr.counter != 0;
         sim->cpu.irq   &= ~0x0002;
     }
 
+    /* Hardware bug: decrement on switch to 20us mode */
+    if (
+        !sim->tmr.t_clk_sel &&
+        (value & 0x10)      && /* T-Clk-Sel */
+        sim->tmr.tick20 != 0
+    ) {
+        tmrUpdate(sim, sim->tmr.counter == 0 ?
+            sim->tmr.reload : sim->tmr.counter - 1);
+    }
+
     /* Parse fields */
     sim->tmr.t_clk_sel = value >> 4 & 1;
     sim->tmr.tim_z_int = value >> 3 & 1;
@@ -105,10 +132,8 @@ static void tmrWriteControl(VB *sim, uint8_t value) {
     if (!sim->tmr.tim_z_int)
         sim->cpu.irq &= ~0x0002;
 
-    /* Configure countdowns */
-    sim->tmr.clocks = sim->tmr.t_clk_sel ? 400 : 2000;
-    sim->tmr.until  = sim->tmr.clocks * (sim->tmr.counter == 0 ?
-        (uint32_t) sim->tmr.reload + 1 : sim->tmr.counter);
+    /* Configure state */
+    sim->tmr.until = tmrGetUntil(sim);
 
     /* TODO: Will Z-Stat raise an interrupt when Tim-Z-Int is set? */
 }
@@ -117,12 +142,14 @@ static void tmrWriteControl(VB *sim, uint8_t value) {
 static void tmrWriteHigh(VB *sim, uint8_t value) {
     sim->tmr.reload = (uint16_t) value << 8 | (sim->tmr.reload & 0x00FF);
     tmrUpdate(sim, sim->tmr.reload);
+    sim->tmr.until  = tmrGetUntil(sim);
 }
 
 /* Write to the low data register */
 static void tmrWriteLow(VB *sim, uint8_t value) {
     sim->tmr.reload = (sim->tmr.reload & 0xFF00) | value;
     tmrUpdate(sim, sim->tmr.reload);
+    sim->tmr.until  = tmrGetUntil(sim);
 }
 
 

core/vb.c

@@ -8,8 +8,11 @@
 
 /*********************************** Types ***********************************/
 
-/* Output image */
-typedef uint8_t Pixels[2][384*224];
+/* VIP BG map cell */
+typedef struct {
+    uint8_t *palette; /* Points to a VB.vip.gplt */
+    uint8_t *pixels;  /* Points to a VB.vip.characters */
+} Cell;
 
 /* VSU channel */
 typedef struct {
@@ -64,9 +67,58 @@ typedef struct {
     } wave;
 
     /* Other state */
-    uint32_t clocks; /* Clocks until next sample */
+    uint32_t clocks;  /* Clocks until next wave or noise sample */
+    uint8_t  freqmod; /* Frequency modifications are active */
+    uint32_t until;   /* Clocks until channel component update */
 } Channel;
 
+/* VIP character (hflp << 1 | vflp) */
+typedef uint8_t Character[4][64];
+
+/* VIP object */
+typedef struct {
+    Cell    cell; /* BG map-like attributes */
+    int16_t jp;   /* Parallax */
+    int16_t jx;   /* Screen base X */
+    int16_t jy;   /* Screen Y */
+    uint8_t lron; /* Visible in left and right images */
+} Object;
+
+/* Output image */
+typedef uint8_t Pixels[2][384*224];
+
+/* VIP world */
+typedef struct {
+
+    /* Attributes */
+    uint8_t  bgm;       /* Mode */
+    uint8_t  end;       /* Control world */
+    int16_t  gp;        /* World parallax */
+    int16_t  gx;        /* World base X */
+    int16_t  gy;        /* World Y */
+    int16_t  mx;        /* Scroll base X */
+    int16_t  mp;        /* Scroll parallax */
+    int16_t  my;        /* Scroll Y */
+    uint8_t  over;      /* Use overplane */
+    Cell    *overplane; /* Overplane cell */
+
+    /* Non-attributes */
+    Cell    *bg[64];    /* Background arrangement */
+    int32_t  bgHeight;  /* Height of background in pixels */
+    uint32_t bgMaskX;   /* Horizontal background mask */
+    uint32_t bgMaskY;   /* Vertical background mask */
+    uint32_t bgShift;   /* Bits to shift when selecting a BG map */
+    int32_t  bgWidth;   /* Width of background in pixels */
+    uint32_t hAffine;   /* H for affine mode */
+    uint32_t hNaffine;  /* H for not affine mode */
+    uint32_t height;    /* Height of world in pixels */
+    uint8_t  lron;      /* Visible in left and right images */
+    uint32_t paramBase; /* H-bias and affine parameter address */
+    uint32_t wAffine;   /* W for affine mode */
+    uint32_t wNaffine;  /* W for not affine mode */
+    uint32_t width;     /* Width of world in pixels */
+} World;
+
 /* Simulation state */
 struct VB {
 
@@ -199,6 +251,7 @@ struct VB {
         uint32_t clocks;  /* Master clocks to wait */
         uint16_t counter; /* Current counter value */
         uint16_t reload;  /* Reload counter value */
+        uint8_t  tick20;  /* Current 20-microsecond tick */
         uint32_t until;   /* Clocks until interrupt condition */
     } tmr;
 
@@ -278,7 +331,11 @@ struct VB {
         Pixels   shadow;            /* Drawing shadow image, column-major */
 
         /* Other state */
-        uint8_t ram[0x40000]; /* Video memory */
+        Cell      cells[0x10000];   /* Pre-computed BG map attributes */
+        Character characters[2048]; /* Pre-computed character pixels */
+        Object    objects[1024];    /* Pre-computed object attributes */
+        uint8_t   ram[0x40000];     /* Video memory */
+        World     worlds[32];       /* Pre-computed world attributes */
     } vip;
 
     /* VSU */
@@ -643,6 +700,7 @@ VBAPI vbOnWrite vbGetWriteCallback(VB *sim) {
 VBAPI VB* vbInit(VB *sim) {
     sim->cart.ram        = NULL;
     sim->cart.rom        = NULL;
+    sim->ph.enabled      = 0;
     sim->vsu.out.samples = NULL;
     sim->onExecute       = NULL;
     sim->onFetch         = NULL;
@@ -652,7 +710,7 @@ VBAPI VB* vbInit(VB *sim) {
     sim->onSamples       = NULL;
     sim->onWrite         = NULL;
     sim->peer            = NULL;
-    sim->ph.enabled      = 0;
+    sim->tag             = NULL;
     vbReset(sim);
     return sim;
 }
@@ -716,28 +774,28 @@ VBAPI int vbSetCartROM(VB *sim, void *rom, uint32_t size) {
 /* Specify a new exception callback handler */
 VBAPI vbOnException vbSetExceptionCallback(VB *sim, vbOnException callback) {
     vbOnException prev = sim->onException;
-    sim->onException = callback;
+    sim->onException   = callback;
     return prev;
 }
 
 /* Specify a new execute callback handler */
 VBAPI vbOnExecute vbSetExecuteCallback(VB *sim, vbOnExecute callback) {
     vbOnExecute prev = sim->onExecute;
-    sim->onExecute = callback;
+    sim->onExecute   = callback;
     return prev;
 }
 
 /* Specify a new fetch callback handler */
 VBAPI vbOnFetch vbSetFetchCallback(VB *sim, vbOnFetch callback) {
     vbOnFetch prev = sim->onFetch;
-    sim->onFetch = callback;
+    sim->onFetch   = callback;
     return prev;
 }
 
 /* Specify a new frame callback handler */
 VBAPI vbOnFrame vbSetFrameCallback(VB *sim, vbOnFrame callback) {
     vbOnFrame prev = sim->onFrame;
-    sim->onFrame = callback;
+    sim->onFrame   = callback;
     return prev;
 }
 
@@ -749,7 +807,7 @@ VBAPI uint16_t vbSetKeys(VB *sim, uint16_t keys) {
 /* Specify a new link callback handler */
 VBAPI vbOnLink vbSetLinkCallback(VB *sim, vbOnLink callback) {
     vbOnLink prev = sim->onLink;
-    sim->onLink = callback;
+    sim->onLink   = callback;
     return prev;
 }
 
@@ -774,6 +832,8 @@ VBAPI int vbSetOption(VB *sim, int key, int value) {
 VBAPI void vbSetPeer(VB *sim, VB *peer) {
     if (sim->peer == peer)
         return;
+    if (sim->peer != NULL)
+        sim->peer->peer = NULL;
     sim->peer = peer;
     if (peer == NULL)
         return;
@@ -784,6 +844,7 @@ VBAPI void vbSetPeer(VB *sim, VB *peer) {
 
 /* Specify a new value for the program counter */
 VBAPI uint32_t vbSetProgramCounter(VB *sim, uint32_t value) {
+    sim->cpu.clocks    = 0;
     sim->cpu.operation = CPU_FETCH;
     sim->cpu.pc        = sim->cpu.nextPC = value & 0xFFFFFFFE;
     sim->cpu.step      = 0;
@@ -798,7 +859,7 @@ VBAPI int32_t vbSetProgramRegister(VB *sim, unsigned index, int32_t value) {
 /* Specify a new read callback handler */
 VBAPI vbOnRead vbSetReadCallback(VB *sim, vbOnRead callback) {
     vbOnRead prev = sim->onRead;
-    sim->onRead = callback;
+    sim->onRead   = callback;
     return prev;
 }
 
@@ -829,7 +890,7 @@ VBAPI uint32_t vbSetSystemRegister(VB *sim, unsigned index, uint32_t value) {
 /* Specify a new write callback handler */
 VBAPI vbOnWrite vbSetWriteCallback(VB *sim, vbOnWrite callback) {
     vbOnWrite prev = sim->onWrite;
-    sim->onWrite = callback;
+    sim->onWrite   = callback;
     return prev;
 }
 
@@ -841,7 +902,7 @@ VBAPI size_t vbSizeOf() {
 /* Specify a simulation's userdata pointer */
 VBAPI void* vbSetUserData(VB *sim, void *tag) {
     void *prev = sim->tag;
-    sim->tag = tag;
+    sim->tag   = tag;
     return prev;
 }
 

core/vb.h

@@ -84,6 +84,24 @@ extern "C" {
 /* Option keys */
 #define VB_PSEUDO_HALT 0
 
+/* Controller buttons */
+#define VB_PWR 0x0001
+#define VB_SGN 0x0002
+#define VB_A   0x0004
+#define VB_B   0x0008
+#define VB_RT  0x0010
+#define VB_LT  0x0020
+#define VB_RU  0x0040
+#define VB_RR  0x0080
+#define VB_LR  0x0100
+#define VB_LL  0x0200
+#define VB_LD  0x0400
+#define VB_LU  0x0800
+#define VB_STA 0x1000
+#define VB_SEL 0x2000
+#define VB_RL  0x4000
+#define VB_RD  0x8000
+
 
 
 /*********************************** Types ***********************************/

core/vip.c

@@ -56,37 +56,18 @@ static const uint8_t BRIGHT8[] = {
 
 /*********************************** Types ***********************************/
 
-/* World attribtues per eye */
+/* Intersection of the screen and a world rectangle */
 typedef struct {
-    int32_t bp;          /* BG source parallax */
-    int32_t left, right; /* Window bounds */
-    int32_t wx;          /* World horizontal position */
-} EyeAttribs;
-
-/* Parsed world attributes */
-typedef struct {
-    int32_t  base;        /* Base BG map index */
-    uint8_t *bg;          /* Background template */
-    int32_t  bgm;         /* World type */
-    int32_t  bgw, bgh;    /* Background dimension masks */
-    int32_t  bottom, top; /* Window bounds */
-    int32_t  gx, gp, gy;  /* World screen position */
-    int32_t  mx, mp, my;  /* Background scroll */
-    uint8_t *over;        /* Overplane character */
-    uint32_t params;      /* Line parameters address */
-    int32_t  scx, scy;    /* Background dimensions */
-    int32_t  w, h;        /* Window size */
-} WorldAttribs;
+    int32_t x1; /* Left edge inclusive */
+    int32_t x2; /* Right edge exclusive */
+    int32_t y1; /* Top edge inclusive */
+    int32_t y2; /* Bottom edge exclusive */
+} Window;
 
 
 
 /***************************** Module Functions ******************************/
 
-/* Retrieve a pointer to character data in host memory */
-static uint8_t* vipCharacter(VB *sim, uint32_t c) {
-    return &sim->vip.ram[0x06000 | (c << 6 & 0x18000) | (c << 4 & 0x01FF0)];
-}
-
 /* Read a palette */
 static int32_t vipReadPalette(uint8_t *entries) {
     return entries[3] << 6 | entries[2] << 4 | entries[1] << 2;
@@ -244,6 +225,178 @@ static int32_t vipReadIO(VB *sim, uint32_t address, int type) {
     value;
 }
 
+/* Write into BG map cell memory */
+static void vipWriteCell(VB *sim, uint32_t offset, int type, int32_t value) {
+    Cell *cell;
+
+    /* Adjustments for byte and word writes */
+    switch (type) {
+        case VB_S8:
+        case VB_U8:
+            value = offset & 1 ?
+                value << 8 |           sim->vip.ram[0x20001 ^ offset] :
+                value      | (int32_t) sim->vip.ram[0x20001 | offset] << 8
+            ;
+            break;
+        case VB_S32:
+            vipWriteCell(sim, offset + 2, VB_U16, value >> 16);
+            break;
+    }
+
+    /* Update pixel pointer */
+    cell          = &sim->vip.cells[offset >> 1];
+    cell->palette = sim->vip.gplt[value >> 14 & 3];
+    cell->pixels  = sim->vip.characters[value & 0x07FF][value >> 12 & 3];
+}
+
+/* Write into character memory */
+static void vipWriteChr(VB *sim, uint32_t offset, int type, int32_t value) {
+    Character *chr;        /* Pixel state */
+    int        b, l, r, t; /* Pixel bounds */
+    int        x, y, X, Y; /* Iterators */
+
+    /* Byte advance by data type */
+    static const uint8_t HORZ[] = { 4, 4, 8, 8,  8 };
+    static const uint8_t VERT[] = { 8, 8, 8, 8, 16 };
+
+    /* Working variables */
+    chr = &sim->vip.characters[offset >> 4];
+    l   = (offset & 0x1) << 2;
+    t   = (offset & 0xE) << 2;
+    r   = l + HORZ[type];
+    b   = t + VERT[type];
+
+    /* Process all pixels */
+    for (y = t, Y = 56 - y; y < b; y += 8, Y -= 8)
+    for (x = l, X =  7 - x; x < r; x += 1, X -= 1, value >>= 2) {
+        (*chr)[0][y | x] = (*chr)[1][Y | x] =
+        (*chr)[2][y | X] = (*chr)[3][Y | X] = value & 3;
+    }
+
+}
+
+/* Write into object attribute memory */
+static void vipWriteObject(VB *sim, uint32_t offset, int type, int32_t value) {
+    Object *obj; /* Object state */
+
+    /* Adjustments for byte and word writes */
+    switch (type) {
+        case VB_S8:
+        case VB_U8:
+            value = offset & 1 ?
+                value << 8 |           sim->vip.ram[0x3E001 ^ offset] :
+                value      | (int32_t) sim->vip.ram[0x3E001 | offset] << 8
+            ;
+            break;
+        case VB_S32:
+            vipWriteObject(sim, offset + 2, VB_U16, value >> 16);
+            break;
+    }
+
+    /* Processing by offset */
+    obj = &sim->vip.objects[offset >> 3];
+    switch (offset >> 1 & 3) {
+        case 0: obj->jx = SignExtend(value, 10); break;
+        case 1:
+            obj->jp   = SignExtend(value, 10);
+            obj->lron = value >> 14 & 3;
+            break;
+        case 2:
+            value = (int8_t) value;
+            obj->jy = value > -8 ? value : value & 0xFF;
+            break;
+        case 3:
+            obj->cell.palette = sim->vip.jplt[value >> 14 & 3];
+            obj->cell.pixels  =
+                sim->vip.characters[value & 0x07FF][value >> 12 & 3];
+    }
+
+}
+
+/* Write into world attribute memory */
+static void vipWriteWorld(VB *sim, uint32_t offset, int type, int32_t value) {
+    uint32_t base;  /* Base BG map index */
+    uint8_t *bg;    /* Background template */
+    uint32_t count; /* Number of BG maps in background */
+    World   *world; /* World state */
+    uint32_t z;     /* Iterator */
+
+    /* Adjustments for byte and word writes */
+    switch (type) {
+        case VB_S8:
+        case VB_U8:
+            value = offset & 1 ?
+                value << 8 |           sim->vip.ram[0x3D801 ^ offset] :
+                value      | (int32_t) sim->vip.ram[0x3D801 | offset] << 8
+            ;
+            break;
+        case VB_S32:
+            vipWriteWorld(sim, offset + 2, VB_U16, value >> 16);
+            break;
+    }
+
+    /* Processing by offset */
+    world = &sim->vip.worlds[offset >> 5];
+    switch (offset >> 1 & 15) {
+        case 0:
+
+            /* Parse attributes */
+            world->lron = value >> 14 & 3;
+            world->bgm  = value >> 12 & 3;
+            world->over = value >>  7 & 1;
+            world->end  = value >>  6 & 1;
+
+            /* Update background fields */
+            z               = value >> 10 & 3;
+            world->bgMaskX  =  (1 << z) - 1;
+            world->bgWidth  = 512 << z;
+            world->bgShift  = z;
+            z               = value >>  8 & 3;
+            world->bgMaskY  =  (1 << z) - 1;
+            world->bgHeight = 512 << z;
+
+            /* Update world dimensions */
+            if (world->bgm != 2) {
+                world->height = world->hNaffine;
+                world->width  = world->wNaffine;
+            } else {
+                world->height = world->hAffine;
+                world->width  = world->wAffine;
+            }
+
+            /* Update background arrangement */
+            count = (world->bgMaskX + 1) * (world->bgMaskY + 1);
+            base  = value & 15 & ~(count > 8 ? 7 : count - 1);
+            bg    = (uint8_t *) BG_TEMPLATES[value >> 8 & 15];
+            for (z = 0; z < count; z++)
+                world->bg[z] = &sim->vip.cells[(base + bg[z]) << 12];
+            break;
+
+        case 1: world->gx = SignExtend(value, 10); break;
+        case 2: world->gp = SignExtend(value, 10); break;
+        case 3: world->gy = (int16_t) value;       break;
+        case 4: world->mx = SignExtend(value, 13); break;
+        case 5: world->mp = SignExtend(value, 15); break;
+        case 6: world->my = SignExtend(value, 13); break;
+        case 7: /* W */
+            value = SignExtend(value, 13) + 1;
+            world->wNaffine = value < 0 ? 0 : value;
+            value = SignExtend(value, 10) + 1;
+            world->wAffine  = value < 0 ? 0 : value;
+            world->width = world->bgm != 2 ? world->wNaffine : world->wAffine;
+            break;
+        case 8: /* H */
+            value = (int16_t) value + 1;
+            world->hNaffine = value < 8 ? 8 : value;
+            world->hAffine  = value < 0 ? 0 : value;
+            world->height = world->bgm != 2 ? world->hNaffine : world->hAffine;
+            break;
+        case  9: world->paramBase = 0x20000|(uint32_t)(uint16_t)value<<1;break;
+        case 10: world->overplane = &sim->vip.cells[(uint16_t) value];   break;
+    }
+
+}
+
 /* Write a typed value to an I/O register */
 static void vipWriteIO(
     VB *sim, uint32_t address, int type, int32_t value, int debug) {
@@ -328,10 +481,12 @@ static void vipWriteIO(
             break;
 
         case 0x5F830>>1: /* CTA */
-            if ((mask & 0xFF00) == 0)
-                sim->vip.cta.cta_r = value >> 8;
-            if ((mask & 0x00FF) == 0)
-                sim->vip.cta.cta_l = value;
+            if (debug) {
+                if ((mask & 0xFF00) == 0)
+                    sim->vip.cta.cta_r = value >> 8;
+                if ((mask & 0x00FF) == 0)
+                    sim->vip.cta.cta_l = value;
+            }
             break;
 
         case 0x5F842>>1: /* XPCTRL */
@@ -627,298 +782,311 @@ static int vipEmulateDisplay(VB *sim, uint32_t clocks) {
 
 /****************************** Pixel Processor ******************************/
 
-/* Parse eye attributes and test window bounds */
-static int vipParseEye(WorldAttribs *wttr, EyeAttribs *ettr, int eye) {
+/* Draw a cell into shadow memory */
+static void vipDrawCell(uint8_t *shadow, Window *wnd,
+    Cell *cell, int32_t x, int32_t y) {
+    uint8_t *col, *row;          /* Output pixel */
+    uint8_t  pixel;              /* Character pixel value */
+    int32_t  px1, px2, py1, py2; /* Pixel bounds in cell */
+    int32_t  px, py;             /* Pixel origin in cell */
 
-    /* Validate the world isn't right of frame */
-    ettr->wx = wttr->gx - (eye == 0 ? wttr->gp : -wttr->gp);
-    if (ettr->wx > 383)
-        return 1;
-    ettr->left = ettr->wx < 0 ? 0 : ettr->wx;
+    /* Identify the visible pixels */
+    py1 = y     > wnd->y1 ? y     : wnd->y1;
+    py2 = y + 8 < wnd->y2 ? y + 8 : wnd->y2;
+    px1 = x     > wnd->x1 ? x     : wnd->x1;
+    px2 = x + 8 < wnd->x2 ? x + 8 : wnd->x2;
 
-    /* Validate the world isn't left of frame */
-    ettr->right = ettr->wx + wttr->w - 1;
-    if (ettr->right < 0)
-        return 1;
-    if (ettr->right > 383)
-        ettr->right = 383;
-
-    /* BG source parallax */
-    if (wttr->bgm != 2)
-        ettr->bp = eye == 0 ? -wttr->mp : wttr->mp;
-
-    return 0;
-}
-
-/* Parse world attributes and test window bounds */
-static int vipParseWorld(VB*sim,uint8_t*world,uint16_t bits,WorldAttribs*attr){
-    int32_t z; /* Scratch */
-
-    /* Validate the world isn't below the frame */
-    attr->gy = busReadBuffer(world + 6, VB_S16);
-    if (attr->gy > 223)
-        return 1;
-
-    /* Validate the world isn't above the frame, and height is positive */
-    attr->bgm = bits >> 12 & 3;
-    attr->h   = busReadBuffer(world + 16, VB_S16) + 1;
-    z         = attr->bgm == 2 ? 0 : 8;
-    if (attr->h < z)
-        attr->h = z;
-    if (attr->h == 0)
-        return 1;
-    attr->bottom = attr->gy + attr->h - 1;
-    attr->top    = (int32_t) sim->vip.xp.sbcount << 3;
-    if (attr->bottom < attr->top)
-        return 1;
-    if (attr->bottom > 223)
-        attr->bottom = 223;
-    if (attr->top < attr->gy)
-        attr->top = attr->gy;
-
-    /* Validate width is positive */
-    attr->w = SignExtend(busReadBuffer(world + 14, VB_U16),
-        attr->bgm == 2 ? 10 : 13) + 1;
-    if (attr->w < 1)
-        return 1;
-
-    /* Parse attributes */
-    attr->bg   = (uint8_t *) BG_TEMPLATES[bits >> 8 & 15];
-    attr->gx   = SignExtend(busReadBuffer(world + 2, VB_U16), 10);
-    attr->gp   = SignExtend(busReadBuffer(world + 4, VB_U16), 10);
-    attr->over = (bits & 0x0080) == 0 ? NULL :
-        &sim->vip.ram[0x00020000 | busReadBuffer(world + 10, VB_U16) << 1];
-    attr->scx  = bits >> 10 & 3;
-    attr->scy  = bits >>  8 & 3;
-    attr->bgw  = (1 << attr->scx) - 1;
-    attr->bgh  = (1 << attr->scy) - 1;
-    z = attr->scx + attr->scy;
-    attr->base = bits & 15 & ~((1 << (z < 3 ? z : 3)) - 1);
-    if (attr->bgm != 2) {
-        attr->mx = SignExtend(busReadBuffer(world +  8, VB_U16), 13);
-        attr->mp = SignExtend(busReadBuffer(world + 10, VB_U16), 15);
-        attr->my = SignExtend(busReadBuffer(world + 12, VB_U16), 13);
-    }
-    if (attr->bgm != 0) {
-        attr->params =
-            0x20000 +
-            (attr->top - attr->gy) * (attr->bgm == 1 ? 4 : 16) +
-            ((uint32_t) busReadBuffer(world + 18, VB_U16) << 1)
-        ;
+    /* Process all columns of pixels */
+    col = &shadow[px1 * 224 + py1];
+    for (px = px1; px < px2; px++, col += 224)
+    for (py = py1, row = col; py < py2; py++, row++) {
+        pixel = cell->pixels[(py - y) << 3 | (px - x)];
+        if (pixel != 0)
+            *row = cell->palette[pixel];
     }
 
-    return 0;
 }
 
-/* Draw an object group into shadow memory */
-static void vipDrawObjects(VB *sim, int group) {
-    uint8_t *dest;       /* Pointer to object position in shadow memory */
-    int      fx;         /* Output horizontal position */
-    int      fy;         /* Output vertical position */
-    uint8_t *obj;        /* Pointer to object attributes in host memory */
-    int32_t  ox;         /* Eye horizontal position */
-    int      pixel;      /* Character input pixel */
-    int      start;      /* Index of first object in group */
-    int      stop;       /* Index of last object in group */
-    int      sx;         /* Input horizontal position */
-    int      sy;         /* Input vertical position */
-    int32_t  top;        /* Window boundary */
-    int      i, o, x, y; /* Iterators */
+/* Draw a BG map into shadow memory */
+static void vipDrawBGMap(uint8_t *shadow, Window *wnd,
+    uint8_t over, Cell *map, int32_t x, int32_t y) {
+    Cell   *col, *row;          /* Source cell */
+    int32_t cx1, cx2, cy1, cy2; /* Cell bounds in BG map pixels */
+    int32_t cx, cy;             /* Cell origin in BG map pixels */
 
-    /* Object attributes */
-    uint32_t attr1;      /* Attribute bits */
-    uint32_t attr2;      /* Attribute bits */
-    int      jhflp;      /* Is flipped horizontally */
-    int32_t  jp;         /* Stereo parallax */
-    int      jvflp;      /* Is flipped vetically */
-    int32_t  jx;         /* Base horizontal position */
-    int32_t  jy;         /* Vertical position */
-    uint8_t *plt;        /* Palette */
-    uint8_t *src;        /* Pointer to character source data in host memory */
+    /* Identify the visible cells */
+    cy1 = (wnd->y1-y  ) & ~7; if (cy1 < 0) cy1 = 0; if (cy1 > 512) cy1 = 512;
+    cy2 = (wnd->y2-y+7) & ~7; if (cy2 < 0) cy2 = 0; if (cy2 > 512) cy2 = 512;
+    cx1 = (wnd->x1-x  ) & ~7; if (cx1 < 0) cx1 = 0; if (cx1 > 512) cx1 = 512;
+    cx2 = (wnd->x2-x+7) & ~7; if (cx2 < 0) cx2 = 0; if (cx2 > 512) cx2 = 512;
 
-    /* Process all objects in the group */
-    start = group == 0 ? 0 : (sim->vip.spt[group - 1] + 1) & 1023;
-    stop  = sim->vip.spt[group];
-    top   = (int32_t) sim->vip.xp.sbcount << 3;
-    for (o = stop; o != -1; o = o == start ? -1 : (o - 1) & 1023) {
-        obj = &sim->vip.ram[0x3E000 | o << 3];
+    /* Process all cells as overplane */
+    if (over) {
+        for (cy = cy1; cy < cy2; cy += 8)
+        for (cx = cx1; cx < cx2; cx += 8)
+            vipDrawCell(shadow, wnd, map, x + cx, y + cy);
+        return;
+    }
 
-        /* Validate object is enabled */
-        attr1 = busReadBuffer(obj + 2, VB_U16);
-        if ((attr1 & 0xC000) == 0) /* JLON, JRON */
+    /* Process all cells normally */
+    row = &map[cy1 << 3 | cx1 >> 3];
+    for (cy = cy1           ; cy < cy2; cy += 8, row += 64)
+    for (cx = cx1, col = row; cx < cx2; cx += 8, col++)
+        vipDrawCell(shadow, wnd, col, x + cx, y + cy);
+}
+
+/* Draw a background into shadow memory */
+static void vipDrawBackground(uint8_t *shadow, Window *wnd,
+    World *world, int32_t x, int32_t y) {
+    int32_t bx1, bx2, by1, by2; /* BG map bounds in background pixels */
+    int32_t bx, by;             /* BG map origin in background pixels */
+
+    /* Identify the visible BG maps */
+    by1 = (wnd->y1 - y    ) & ~511;
+    by2 = (wnd->y2 - y - 1) & ~511;
+    bx1 = (wnd->x1 - x    ) & ~511;
+    bx2 = (wnd->x2 - x - 1) & ~511;
+
+    /* Process all rows of BG maps */
+    for (by = by1; by <= by2; by += 512) {
+
+        /* Row is out of bounds */
+        if (world->over && (by < 0 || by >= world->bgHeight)) {
+            for (bx = bx1; bx <= bx2; bx++)
+                vipDrawBGMap(shadow, wnd, 1, world->overplane, x + bx, y + by);
             continue;
+        }
 
-        /* Validate Y position */
-        jy = (int8_t) obj[4];
-        if (jy < 7)
-            jy &= 0xFF;
-        if (jy < top - 7 || jy > 223)
-            continue;
+        /* Process all columns of BG maps */
+        for (bx = bx1; bx <= bx2; bx += 512) {
 
-        /* Parse attributes */
-        jx    = SignExtend(busReadBuffer(obj, VB_U16), 10);
-        jp    = SignExtend(attr1, 10);
-        attr2 = busReadBuffer(obj + 6, VB_U16);
-        jhflp = attr2 >> 13 & 1;
-        jvflp = attr2 >> 12 & 1;
-
-        /* Locate palette and character state in host memory */
-        plt = sim->vip.jplt[attr2 >> 14];
-        src = vipCharacter(sim, attr2); 
-
-        /* Draw the character */
-        for (i = 0; i < 2; i++) {
-            if ((attr1 >> (15 - i) & 1) == 0) /* J*ON */
+            /* Column is out of bounds */
+            if (world->over && (bx < 0 || bx >= world->bgWidth)) {
+                vipDrawBGMap(shadow, wnd, 1, world->overplane, x + bx, y + by);
                 continue;
-            ox   = jx - (i == 0 ? jp : -jp);
-            dest = &sim->vip.shadow[i][ox * 224 + jy];
-
-            /* Draw all columns */
-            for (x = 0; x < 8; x++, dest += 224) {
-                fx = ox + x;
-                if (fx < 0 || fx > 383)
-                    continue;
-                sx = jhflp ? 7 - x : x;
-
-                /* Draw all rows */
-                for (y = 0; y < 8; y++) {
-                    fy = jy + y;
-                    if (fy < top || fy > 223)
-                        continue;
-                    sy    = jvflp ? 7 - y : y;
-                    pixel = src[sy << 1 | sx >> 2] >> ((sx & 3) << 1) & 3;
-                    if (pixel != 0)
-                        dest[y] = plt[pixel]; /* TODO: Research clocks */
-                } /* y */
-
-            } /* x */
-
-        } /* i */
-
-    }
-
-}
-
-/* Draw a background world into shadow memory */
-static void vipDrawWorld(VB *sim, uint8_t *world, uint16_t bits) {
-    uint16_t   bgAttr;  /* BG map cell attributes */
-    int32_t    bx;      /* BG source X */
-    int32_t    by;      /* BG source Y */
-    uint8_t   *cell;    /* Pointer to BG map cell in host memory */
-    uint8_t   *chr;     /* Pointer to character data in host memory */
-    int32_t    cx;      /* BG cell/character source X */
-    int32_t    cy;      /* BG cell/character source Y */
-    uint8_t   *dest;    /* Pointer to output in shadow memory */
-    EyeAttribs ettr;    /* Eye attributes */
-    uint32_t   param;   /* Current line parameter address */
-    int8_t     pixel;   /* Character pixel value */
-    int32_t    i, x, y; /* Iterators */
-
-    /* World attributes */
-    WorldAttribs wttr;  /* Common attributes */
-    int32_t      dx;    /* Affine per-pixel X delta */
-    int32_t      dy;    /* Affine per-pixel Y delta */
-    int32_t      mp;    /* BG source parallax */
-    int32_t      mx;    /* BG source X */
-    int32_t      my;    /* BG source Y */
-    int16_t      hofst; /* H-bias shift */
-
-    /* Working variables */
-    ettr.bp = wttr.mp = wttr.mx = wttr.my = wttr.params = 0;
-
-    /* Parse attributes */
-    if (vipParseWorld(sim, world, bits, &wttr))
-        return; /* Window not in frame */
-
-    /* Draw the world */
-    for (i = 0; i < 2; i++) {
-
-        /* World is not visible */
-        if ((bits & (int32_t) 0x8000 >> i) == 0) /* LON, RON */
-            continue;
-
-        /* Process attributes */
-        if (vipParseEye(&wttr, &ettr, i))
-            continue;
-
-        /* Draw all rows */
-        for (y = wttr.top, param = wttr.params; y <= wttr.bottom; y++) {
-
-            /* Parse line parameters */
-            hofst = 0;
-            mp    = wttr.mp;
-            mx    = wttr.mx;
-            my    = wttr.my;
-            switch (wttr.bgm) {
-                case 1: /* H-bias */
-                    hofst  = SignExtend(vipParam(param | i << 1), 13);
-                    param += 4;
-                    break;
-                case 2: /* Affine */
-                    dx =  (int32_t) (int16_t) vipParam(param|6) << 7;
-                    dy =  (int32_t) (int16_t) vipParam(param|8) << 7;
-                    mp =  (int32_t) (int16_t) vipParam(param|2);
-                    mp = ettr.left - ettr.wx - ((mp < 0) ^ i ? mp : 0);
-                    mx = ((int32_t) (int16_t) vipParam(param  ) << 13) + dx*mp;
-                    my = ((int32_t) (int16_t) vipParam(param|4) << 13) + dy*mp;
-                    param += 16;
             }
 
-            /* Select output in shadow memory */
-            dest = &sim->vip.shadow[i][ettr.left * 224 + y];
+            /* Column is in bounds */
+            vipDrawBGMap(shadow, wnd, 0, world->bg[
+                (by >> 9 & world->bgMaskY) << world->bgShift |
+                (bx >> 9 & world->bgMaskX)
+            ], x + bx, y + by);
+        }
 
-            /* Draw all columns */
-            for (x = ettr.left; x <= ettr.right; x++, dest += 224) {
+    }
 
-                /* Locate the pixel in the background */
-                if (wttr.bgm != 2) { /* Normal, H-bias */
-                    cx  = x - ettr.wx + mx + ettr.bp + hofst;
-                    cy  = y - wttr.gy + my;
-                } else { /* Affine */
-                    cx  = (int16_t) (mx >> 16);
-                    cy  = (int16_t) (my >> 16);
-                    mx += dx;
-                    my += dy;
-                }
+}
 
-                /* Locate the BG map in the background */
-                bx   = SignExtend(cx >> 9, 23);
-                by   = SignExtend(cy >> 9, 23);
-                cell = NULL;
+/* Draw a Normal world into shadow memory */
+static void vipDrawNormal(VB *sim, World *world) {
+    int32_t  mx, my; /* Background origin */
+    Window   wnd;    /* Window bounds in pixels */
+    int      i;      /* Iterator */
 
-                /* BG map is out of bounds */
-                if (
-                    bx < 0 || bx > wttr.bgw ||
-                    by < 0 || by > wttr.bgh
-                ) {
-                    if (wttr.over == NULL) {
-                        bx &= wttr.bgw;
-                        by &= wttr.bgh;
-                    } else cell = wttr.over;
-                }
+    /* No visible content */
+    if (world->width == 0)
+        return;
 
-                /* Locate the cell in the BG map */
-                if (cell == NULL) {
-                    cell = &sim->vip.ram[
-                        0x20000 | ((
-                            wttr.base +
-                            wttr.bg[by << wttr.scx | bx]
-                        ) << 13) |
-                        (cy << 4 & 0x1F80) |
-                        (cx >> 2 & 0x007E)
-                    ];
-                }
+    /* Vertical window bounds */
+    wnd.y1 = (int32_t) sim->vip.xp.sbcount << 3;
+    if (world->gy > wnd.y1)
+        wnd.y1 = world->gy;
+    if (wnd.y1 >= 224)
+        return;
+    wnd.y2 = world->gy + world->height;
+    if (wnd.y2 <= 0)
+        return;
+    my = world->gy - world->my;
+    if (wnd.y1 < 0)
+        wnd.y1 = 0;
+    if (wnd.y2 > 224)
+        wnd.y2 = 224;
 
-                /* Extract the pixel from the character */
-                bgAttr = busReadBuffer(cell, VB_U16);
-                chr    = vipCharacter(sim, bgAttr);
-                cx     = (bgAttr & 0x2000 ? 7 - cx : cx) & 7;
-                cy     = (bgAttr & 0x1000 ? 7 - cy : cy) & 7;
-                pixel  = chr[cy << 1 | cx >> 2] >> ((cx & 3) << 1) & 3;
+    /* Process both eyes */
+    for (i = 0; i < 2; i++) {
 
-                /* Write the pixel into shadow memory */
+        /* Check visibility */
+        if (!(world->lron >> (i ^ 1) & 1))
+            continue;
+
+        /* Horizontal window bounds */
+        wnd.x1 = world->gx + (i == 0 ? -world->gp : world->gp);
+        if (wnd.x1 >= 384)
+            continue;
+        wnd.x2 = wnd.x1 + world->width;
+        if (wnd.x2 <= 0)
+            continue;
+        mx = wnd.x1 - world->mx - (i == 0 ? -world->mp : world->mp);
+        if (wnd.x1 < 0)
+            wnd.x1 = 0;
+        if (wnd.x2 > 384)
+            wnd.x2 = 384;
+
+        /* Draw the background into the window */
+        vipDrawBackground(sim->vip.shadow[i], &wnd, world, mx, my);
+    }
+
+}
+
+/* Draw an H-bias world into shadow memory */
+static void vipDrawHBias(VB *sim, World *world) {
+    int32_t  mx, my; /* Background origin */
+    uint8_t *param;  /* World parameter memory */
+    Window   wnd;    /* Window bounds in pixels */
+    int32_t  y1, y2; /* Vertical window bounds */
+    int      i, y;   /* Iterators */
+
+    /* No visible content */
+    if (world->width == 0)
+        return;
+
+    /* Vertical window bounds */
+    y1 = (int32_t) sim->vip.xp.sbcount << 3;
+    if (world->gy > y1)
+        y1 = world->gy;
+    if (y1 >= 224)
+        return;
+    y2 = world->gy + world->height;
+    if (y2 <= 0)
+        return;
+    my = world->gy - world->my;
+    if (y1 < 0)
+        y1 = 0;
+    if (y2 > 224)
+        y2 = 224;
+
+    /* Process both eyes */
+    for (i = 0; i < 2; i++) {
+
+        /* Check visibility */
+        if (!(world->lron >> (i ^ 1) & 1))
+            continue;
+
+        /* Horizontal window bounds */
+        wnd.x1 = world->gx + (i == 0 ? -world->gp : world->gp);
+        if (wnd.x1 >= 384)
+            continue;
+        wnd.x2 = wnd.x1 + world->width;
+        if (wnd.x2 <= 0)
+            continue;
+        mx = wnd.x1 - world->mx - (i == 0 ? -world->mp : world->mp);
+        if (wnd.x1 < 0)
+            wnd.x1 = 0;
+        if (wnd.x2 > 384)
+            wnd.x2 = 384;
+
+        /* Process all visible lines */
+        param = &sim->vip.ram[world->paramBase +
+            ((y1 - world->gy) << 2) + (i << 1)];
+        for (y = y1; y < y2; y++, param += 2) {
+
+            /* Configure window bounds */
+            wnd.y1 = y;
+            wnd.y2 = y + 1;
+
+            /* Draw the background into the window */
+            vipDrawBackground(sim->vip.shadow[i], &wnd, world,
+                mx + busReadBuffer(param, VB_S16), my);
+        }
+
+    }
+
+}
+
+/* Draw an Affine world into shadow memory */
+static void vipDrawAffine(VB *sim, World *world) {
+    Cell    *cell;               /* Source cell */
+    uint8_t *col, *row;          /* Output pixel */
+    uint8_t  pixel;              /* Character pixel value */
+    uint8_t *param;              /* World parameter memory */
+    int32_t  px, py;             /* Pixel source coordinates */
+    int32_t  dx, dy, mp, mx, my; /* Affine parameters */
+    int32_t  wx;                 /* Base world X coordinate */
+    int32_t  x1, x2, y1, y2;     /* Window bounds */
+    int      i, x, y;            /* Iterators */
+
+    /* No visible content */
+    if (world->width == 0 || world->height == 0)
+        return;
+
+    /* Vertical window bounds */
+    y1 = (int32_t) sim->vip.xp.sbcount << 3;
+    if (world->gy > y1)
+        y1 = world->gy;
+    if (y1 >= 224)
+        return;
+    y2 = world->gy + world->height;
+    if (y2 <= 0)
+        return;
+    if (y1 < 0)
+        y1 = 0;
+    if (y2 > 224)
+        y2 = 224;
+
+    /* Process both eyes */
+    for (i = 0; i < 2; i++) {
+
+        /* Check visibility */
+        if (!(world->lron >> (i ^ 1) & 1))
+            continue;
+
+        /* Horizontal window bounds */
+        x1 = world->gx + (i == 0 ? -world->gp : world->gp);
+        if (x1 >= 384)
+            continue;
+        x2 = x1 + world->width;
+        if (x2 <= 0)
+            continue;
+        wx = x1;
+        if (x1 < 0)
+            x1 = 0;
+        if (x2 > 384)
+            x2 = 384;
+        wx = x1 - wx;
+
+        /* Process all visible rows */
+        param = &sim->vip.ram[world->paramBase | (y1 - world->gy) << 4];
+        row   = &sim->vip.shadow[i][x1 * 224 + y1];
+        for (y = y1; y < y2; y++, param += 16, row++) {
+
+            /* Parse line parameters */
+            mx = (int32_t) busReadBuffer(param + 0, VB_S16) << 6;
+            mp = (int32_t) busReadBuffer(param + 2, VB_S16);
+            my = (int32_t) busReadBuffer(param + 4, VB_S16) << 6;
+            dx = (int32_t) busReadBuffer(param + 6, VB_S16);
+            dy = (int32_t) busReadBuffer(param + 8, VB_S16);
+
+            /* Adjust left-edge parameters */
+            if ((mp < 0) ^ i) {
+                mx += dx * (wx - mp);
+                my += dy * (wx - mp);
+            } else {
+                mx += dx * wx;
+                my += dy * wx;
+            }
+
+            /* Process all visible columns */
+            col = row;
+            for (x = x1; x < x2; x++, mx += dx, my += dy, col += 224) {
+                px = (int16_t) (mx >> 9);
+                py = (int16_t) (my >> 9);
+
+                /* Overplane */
+                if (world->over && (
+                    px < 0 || px >= world->bgWidth ||
+                    py < 0 || py >= world->bgHeight
+                )) cell = world->overplane;
+
+                /* Regular */
+                else cell = &world->bg[
+                    (py >> 9 & world->bgMaskY) << world->bgShift |
+                    (px >> 9 & world->bgMaskX)
+                ][(py << 3 & 0xFC0) | (px >> 3 & 63)];
+
+                /* Sample the pixel */
+                pixel = cell->pixels[(py & 7) << 3 | (px & 7)];
                 if (pixel != 0)
-                    *dest = sim->vip.gplt[bgAttr >> 14 & 3][pixel];
+                    *col = cell->palette[pixel];
 
             } /* x */
 
@@ -928,12 +1096,40 @@ static void vipDrawWorld(VB *sim, uint8_t *world, uint16_t bits) {
 
 }
 
+/* Draw an object group into shadow memory */
+static void vipDrawObjects(VB *sim, int group) {
+    Object *obj;   /* Object state */
+    int     start; /* First object in the group */
+    int     stop;  /* Last object in the group */
+    Window  wnd;   /* Window bounds in pixels */
+    int     i, o;  /* Iterators */
+
+    /* Establish the viewing window */
+    wnd.x1 = 0;
+    wnd.y1 = (int32_t) sim->vip.xp.sbcount << 3;
+    wnd.x2 = 384;
+    wnd.y2 = 224;
+
+    /* Process all objects in the group */
+    start = group == 0 ? 0 : (sim->vip.spt[group - 1] + 1) & 1023;
+    stop  = sim->vip.spt[group];
+    for (o = stop; o != -1; o = o == start ? -1 : (o - 1) & 1023) {
+        obj = &sim->vip.objects[o];
+        for (i = 0; i < 2; i++) {
+            if (!(obj->lron >> (i ^ 1) & 1))
+                continue;
+            vipDrawCell(sim->vip.shadow[i], &wnd, &obj->cell,
+                obj->jx + (i == 0 ? -obj->jp : obj->jp), obj->jy);
+        }
+    }
+
+}
+
 /* Draw the current graphics configuration into shadow memory */
 static void vipRender(VB *sim) {
-    uint16_t  attr;   /* World attribute bits */
     int       group;  /* Next object group index */
     uint16_t *timing; /* Column timing in host memory */
-    uint8_t  *world;  /* World attribute source in host memory */
+    World    *world;  /* World attribute source in host memory */
     int32_t   x, y;   /* Iterators */
 
     /* Erase all pixels */
@@ -943,25 +1139,25 @@ static void vipRender(VB *sim) {
 
     /* Process all worlds */
     group = 3;
-    world = &sim->vip.ram[0x3DBE0]; /* World 31 */
-    for (x = 31; x >= 0; x--, world -= 32) {
-        attr = busReadBuffer(world, VB_U16);
+    for (x = 31; x >= 0; x--) {
+        world = &sim->vip.worlds[x];
 
         /* Non-graphical world */
-        if (attr & 0x0040) /* END */
+        if (world->end)
             break;    /* Control world */
-        if ((attr & 0xC000) == 0) /* LON, RON */
+        if (world->lron == 0)
             continue; /* Dummy world */
 
-        /* Object world */
-        if ((attr >> 12 & 3) == 3) {
-            vipDrawObjects(sim, group);
-            group = (group - 1) & 3;
+        /* Processing by world type */
+        switch (world->bgm) {
+            case 0: vipDrawNormal(sim, world); break;
+            case 1: vipDrawHBias (sim, world); break;
+            case 2: vipDrawAffine(sim, world); break;
+            case 3:
+                vipDrawObjects(sim, group);
+                group = (group - 1) & 3;
         }
 
-        /* Background world */
-        else if (attr & 0xC000) /* LON, RON */
-            vipDrawWorld(sim, world, attr);
     }
 
     /*
@@ -1134,7 +1330,11 @@ static void vipRead(VB *sim, uint32_t address, int type, int32_t *value) {
 
 /* Simulate a hardware reset */
 static void vipReset(VB *sim) {
-    int x, y; /* Iterators */
+    Cell      *cell;  /* BG map cell state */
+    Character *chr;   /* Character state */
+    Object    *obj;   /* Object state */
+    World     *world; /* World state */
+    int        x, y;  /* Iterators */
 
     /* Normal */
     sim->vip.intenb   = 0x0000;
@@ -1159,6 +1359,53 @@ static void vipReset(VB *sim) {
             sim->vip.jplt[x][y] = 0;
         }
     }
+    for (x = 0; x < 0x10000; x++) {
+        cell = &sim->vip.cells[x];
+        cell->palette = sim->vip.gplt[0];
+        cell->pixels  = sim->vip.characters[0][0];
+    }
+    for (x = 0; x < 2048; x++) {
+        chr = &sim->vip.characters[x];
+        for (y = 0; y < 64; y++)
+            (*chr)[0][y] = (*chr)[1][y] = (*chr)[2][y] = (*chr)[3][y] = 0;
+    }
+    for (x = 0; x < 32; x++) {
+        world = &sim->vip.worlds[x];
+        world->bgm       = 0;
+        world->end       = 0;
+        world->gp        = 0;
+        world->gx        = 0;
+        world->gy        = 0;
+        world->mx        = 0;
+        world->mp        = 0;
+        world->my        = 0;
+        world->over      = 0;
+        world->overplane = &sim->vip.cells[0];
+        for (y = 0; y < 64; y++)
+            world->bg[0] = world->overplane;
+        world->bgHeight  = 512;
+        world->bgMaskX   = 0;
+        world->bgMaskY   = 0;
+        world->bgShift   = 0;
+        world->bgWidth   = 512;
+        world->hAffine   = 0;
+        world->hNaffine  = 0;
+        world->height    = 8;
+        world->lron      = 0;
+        world->paramBase = 0;
+        world->wAffine   = 0;
+        world->wNaffine  = 0;
+        world->width     = 0;
+    }
+    for (x = 0; x < 1024; x++) {
+        obj = &sim->vip.objects[x];
+        obj->cell.palette = sim->vip.jplt[0];
+        obj->cell.pixels  = sim->vip.characters[0][0];
+        obj->jp           = 0;
+        obj->jx           = 0;
+        obj->jy           = 0;
+        obj->lron         = 0;
+    }
 
     /* Display processor extra (the hardware does not do this) */
     sim->vip.dp.fclk    = 0;
@@ -1206,9 +1453,28 @@ static void vipWrite(VB*sim,uint32_t address,int type,int32_t value,int debug){
     address &= 0x0007FFFF;
 
     /* RAM */
-    if (address < 0x40000)
+    if (address < 0x40000) {
         busWriteBuffer(&sim->vip.ram[address], type, value);
 
+        /* Character memory */
+        if ((address & 0x26000) == 0x06000) {
+            address = (address & 0x18000) >> 2 | (address & 0x01FFF);
+            vipWriteChr(sim, address, type, value);
+        }
+
+        /* BG map memory */
+        if (address >= 0x20000)
+            vipWriteCell(sim, address & 0x1FFFF, type, value);
+
+        /* World memory */
+        if ((address & 0x3FC00) == 0x3D800)
+            vipWriteWorld(sim, address &0x003FF, type, value);
+
+        /* Object memory */
+        if (address >= 0x3E000)
+            vipWriteObject(sim, address & 0x01FFF, type, value);
+    }
+
     /* Unmapped */
     else if (address < 0x5E000)
         ;
@@ -1223,6 +1489,7 @@ static void vipWrite(VB*sim,uint32_t address,int type,int32_t value,int debug){
 
     /* Mirrors of character memory */
     else {
+        vipWriteChr(sim, address & 0x07FFF, type, value);
         address = 0x06000 | (address << 2 & 0x18000) | (address & 0x01FFF);
         busWriteBuffer(&sim->vip.ram[address], type, value);
     }

core/vsu.c

@@ -74,100 +74,57 @@ static void vsuNextFreqMod(VB *sim, Channel *chan) {
 }
 
 /* Process one channel */
-static void vsuEmulateChannel(VB *sim, int index, uint32_t clocks) {
-    uint32_t bit;     /* Pseudorandom bit */
-    Channel *chan;    /* Channel handle */
-    int      freqmod; /* Frequency modifications enabled */
-    uint32_t until;   /* Clocks to process sub-channel components */
+static void vsuEmulateChannel(VB *sim, Channel *chan) {
+    uint32_t bit; /* Pseudorandom bit */
 
-    /* Select channel */
-    chan = &sim->vsu.channels[index];
-
-    /* Channel is disabled */
-    if (!chan->int_.enb)
+    /* Automatic shutoff */
+    if (chan->int_.auto_ && chan->int_.clocks == 0) {
+        chan->int_.enb = 0;
         return;
+    }
 
-    /* Process all clocks */
-    do {
+    /* Next input sample */
+    if (chan->clocks == 0) {
 
-        /* Frequency modifications are active */
-        freqmod = 
-            index == 4           &&        /* Channel 5 */
-            sim->vsu.freqmod.enb &&        /* Modifications enabled */
-            sim->vsu.freqmod.interval != 0 /* Modifications valid */
-        ;
+        /* Wave */
+        if (chan != &sim->vsu.channels[5]) {
+            chan->clocks =  4 * (2048 - (uint32_t) chan->freq.current);
+            chan->wave.sample = (chan->wave.sample + 1) & 31;
+        }
 
-        /* Clocks until next state change */
-        until = clocks;
-        if (chan->clocks < until)
-            until = chan->clocks;
-        if (chan->env.enb && chan->env.clocks < until)
-            until = chan->env.clocks;
-        if (chan->int_.auto_ && chan->int_.clocks < until)
-            until = chan->int_.clocks;
-        if (freqmod && sim->vsu.freqmod.clocks < until)
-            until = sim->vsu.freqmod.clocks;
+        /* Noise */
+        else {
+            chan->clocks = 40 * (2048 - (uint32_t) chan->freq.current);
+            bit = ((
+                sim->vsu.noise.register_ >> NOISE_TAPS[sim->vsu.noise.tap]^
+                sim->vsu.noise.register_ >> 7
+            ) & 1) ^ 1;
+            sim->vsu.noise.register_ = bit |
+                (sim->vsu.noise.register_ << 1 & 0x7FFE);
+        }
 
-        /* Manage clocks */
-        clocks       -= until;
-        chan->clocks -= until;
-        if (chan->env.enb)
-            chan->env.clocks -= until;
-        if (chan->int_.auto_)
-            chan->int_.clocks -= until;
-        if (freqmod)
-            sim->vsu.freqmod.clocks -= until;
+    }
 
-        /* Automatic shutoff */
-        if (chan->int_.auto_ && chan->int_.clocks == 0) {
-            chan->int_.enb = 0;
+    /* Envelope modification */
+    if (chan->env.enb && chan->env.clocks == 0) {
+        if (chan->env.dir == 0 && chan->env.value != 0)
+            chan->env.value--;
+        else if (chan->env.dir == 1 && chan->env.value != 15)
+            chan->env.value++;
+        else if (chan->env.rep)
+            chan->env.value = chan->env.reload;
+        chan->env.clocks = ((uint32_t) chan->env.interval + 1) * 307220;
+    }
+
+    /* Frequency modification */
+    if (chan->freqmod && sim->vsu.freqmod.clocks == 0) {
+        chan->freq.current = sim->vsu.freqmod.next;
+        vsuNextFreqMod(sim, chan);
+        if (!chan->int_.enb)
             return;
-        }
-
-        /* Next sample */
-        if (chan->clocks == 0) {
-
-            /* Wave */
-            if (index != 5) {
-                chan->clocks =  4 * (2048 - (uint32_t) chan->freq.current);
-                chan->wave.sample = (chan->wave.sample + 1) & 31;
-            }
-
-            /* Noise */
-            else {
-                chan->clocks = 40 * (2048 - (uint32_t) chan->freq.current);
-                bit = ((
-                    sim->vsu.noise.register_ >> NOISE_TAPS[sim->vsu.noise.tap]^
-                    sim->vsu.noise.register_ >> 7
-                ) & 1) ^ 1;
-                sim->vsu.noise.register_ = bit |
-                    (sim->vsu.noise.register_ << 1 & 0x7FFE);
-            }
-
-        }
-
-        /* Envelope modification */
-        if (chan->env.enb && chan->env.clocks == 0) {
-            if (chan->env.dir == 0 && chan->env.value != 0)
-                chan->env.value--;
-            else if (chan->env.dir == 1 && chan->env.value != 15)
-                chan->env.value++;
-            else if (chan->env.rep)
-                chan->env.value = chan->env.reload;
-            chan->env.clocks = ((uint32_t) chan->env.interval + 1) * 307220;
-        }
-
-        /* Frequency modification */
-        if (freqmod && sim->vsu.freqmod.clocks == 0) {
-            chan->freq.current = sim->vsu.freqmod.next;
-            vsuNextFreqMod(sim, chan);
-            if (!chan->int_.enb)
-                return;
-            sim->vsu.freqmod.clocks = (uint32_t) sim->vsu.freqmod.interval *
-                (sim->vsu.freqmod.clk == 0 ? 19200 : 153600);
-        }
-
-    } while (clocks != 0);
+        sim->vsu.freqmod.clocks = (uint32_t) sim->vsu.freqmod.interval *
+            (sim->vsu.freqmod.clk == 0 ? 19200 : 153600);
+    }
 
 }
 
@@ -230,6 +187,8 @@ static void vsuWriteEV1(VB *sim, int index, uint8_t value) {
             sim->vsu.freqmod.func = value >> 4 & 1;
             sim->vsu.freqmod.rep  = value >> 5 & 1;
             vsuNextFreqMod(sim, chan);
+            chan->freqmod =
+                sim->vsu.freqmod.enb && sim->vsu.freqmod.interval != 0;
             break;
 
         case 5: /* Channel 6 */
@@ -313,6 +272,8 @@ static void vsuWriteSWP(VB *sim, uint8_t value) {
         (sim->vsu.freqmod.clk == 0 ? 19200 : 153600);
     if (clocks < sim->vsu.freqmod.clocks)
         sim->vsu.freqmod.clocks = clocks;
+    sim->vsu.channels[4].freqmod =
+        sim->vsu.freqmod.enb && sim->vsu.freqmod.interval != 0;
 }
 
 
@@ -321,6 +282,8 @@ static void vsuWriteSWP(VB *sim, uint8_t value) {
 
 /* Process component */
 static void vsuEmulate(VB *sim, uint32_t clocks) {
+    Channel *chan;      /* Input channel */
+    uint32_t chantil;   /* Clocks until next channel state update */
     float    i0;        /* Current analog input sample */
     float    o0;        /* Current analog output sample */
     uint16_t output[2]; /* Digital output samples */
@@ -340,12 +303,54 @@ static void vsuEmulate(VB *sim, uint32_t clocks) {
         sim->vsu.clocks -= until;
 
         /* Process all channels */
-        for (x = 0; x < 6; x++)
-            vsuEmulateChannel(sim, x, until);
+        for (x = 0; x < 6; x++) {
+            chan    = &sim->vsu.channels[x];
+            chantil = until;
+
+            /* Process all clocks */
+            while (chan->int_.enb && chantil != 0) {
+
+                /* Determine when the next state change will occur */
+                if (chan->until == 0) {
+
+                    /* Clocks until next state change */
+                    chan->until = chan->clocks;
+                    if (chan->env.enb && chan->env.clocks < chan->until)
+                        chan->until = chan->env.clocks;
+                    if (chan->int_.auto_ && chan->int_.clocks < chan->until)
+                        chan->until = chan->int_.clocks;
+                    if (chan->freqmod && sim->vsu.freqmod.clocks < chan->until)
+                        chan->until = sim->vsu.freqmod.clocks;
+
+                    /* Manage clocks */
+                    chan->clocks -= chan->until;
+                    if (chan->env.enb)
+                        chan->env.clocks -= chan->until;
+                    if (chan->int_.auto_)
+                        chan->int_.clocks -= chan->until;
+                    if (chan->freqmod)
+                        sim->vsu.freqmod.clocks -= chan->until;
+                }
+
+                /* Manage clocks */
+                if (chan->until > chantil) {
+                    chan->until -= chantil;
+                    chantil      = 0;
+                } else {
+                    chantil     -= chan->until;
+                    chan->until  = 0;
+                }
+
+                /* Update channel state */
+                if (chan->until == 0)
+                    vsuEmulateChannel(sim, chan);
+            }
+
+        }
 
         /* Wait for the current sample to finish */
         if (sim->vsu.clocks != 0)
-            continue;
+            return;
 
         /* Compute the output sample */
         output[0] = output[1] = 0;
@@ -369,7 +374,7 @@ static void vsuEmulate(VB *sim, uint32_t clocks) {
                 sim->vsu.out.offset >> 1 < sim->vsu.out.capacity
             ) {
 
-                /* Processing by data type*/
+                /* Processing by data type */
                 switch (sim->vsu.out.type) {
                     case VB_S16:
                         ((int16_t *) sim->vsu.out.samples)
@@ -416,6 +421,8 @@ static void vsuReset(VB *sim) {
     for (x = 0; x < 6; x++) {
         chan = &sim->vsu.channels[x];
         chan->clocks        = 0;
+        chan->freqmod       = 0;
+        chan->until         = 0;
         chan->env.clocks    = 0;
         chan->env.enb       = 0;
         chan->env.dir       = 0;

util/disassembler.c

@@ -1,4 +1,4 @@
-/* This file is included into vb.c and cannot be compiled on its own. */
+/* This file is included into vbu.c and cannot be compiled on its own. */
 #ifdef VBUAPI
 
 
@@ -253,18 +253,24 @@ static void dasmOpDisp26(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
 }
 
 /* Format a 5-bit sign-extended immediate operand */
-static void dasmOpImm5S(char *dest, VBU_DasmLine *line) {
+static void dasmOpImm5S(char *dest, VBU_DasmConfig*config, VBU_DasmLine *line){
+    if (config->immediateNotation == VBU_NUMBER)
+        *dest++ = '#';
     sprintf(dest, "%d", SignExtend(line->code[0], 5));
 }
 
 /* Format a 5-bit zero-filled immediate operand */
-static void dasmOpImm5U(char *dest, VBU_DasmLine *line) {
+static void dasmOpImm5U(char *dest, VBU_DasmConfig*config, VBU_DasmLine *line){
+    if (config->immediateNotation == VBU_NUMBER)
+        *dest++ = '#';
     sprintf(dest, "%d", line->code[0] & 31);
 }
 
 /* Format a 16-bit sign-extended immediate operand */
 static void dasmOpImm16S(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
-    int32_t imm = (int16_t) ((int16_t) line->code[3] << 8 | line->code[2]);
+    int32_t imm    = (int16_t) ((int16_t) line->code[3] << 8 | line->code[2]);
+    if (config->immediateNotation == VBU_NUMBER)
+        *dest++ = '#';
     if (imm >= -256 && imm <= 256) {
         sprintf(dest, "%d", imm);
         return;
@@ -279,6 +285,8 @@ static void dasmOpImm16S(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
 /* Format a 16-bit zero-filled immediate operand */
 static void dasmOpImm16U(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
     uint16_t imm = (uint16_t) line->code[3] << 8 | line->code[2];
+    if (config->immediateNotation == VBU_NUMBER)
+        *dest++ = '#';
     dasmToHex(dest, config, 4, imm);
 }
 
@@ -441,12 +449,6 @@ static VBU_DasmLine* dasmGrow(
     return *lines == NULL ? NULL : &(*lines)[index];
 }
 
-/* Determine the size of an instruction */
-static uint32_t dasmInstSize(VB *sim, uint32_t address) {
-    unsigned opcode = vbRead(sim, address, VB_U16) >> 10 & 63;
-    return opcode < 0x20 || opcode == 0x32 || opcode == 0x36 ? 2 : 4;
-}
-
 /* Format an operand */
 static void dasmOperand(char *dest, VBU_DasmConfig *config,
     VBU_DasmLine *line, uint8_t type) {
@@ -454,8 +456,8 @@ static void dasmOperand(char *dest, VBU_DasmConfig *config,
         case DASM_BCOND : dasmOpBCOND (dest, config, line); break;
         case DASM_DISP9 : dasmOpDisp9 (dest, config, line); break;
         case DASM_DISP26: dasmOpDisp26(dest, config, line); break;
-        case DASM_IMM5S : dasmOpImm5S (dest,         line); break;
-        case DASM_IMM5U : dasmOpImm5U (dest,         line); break;
+        case DASM_IMM5S : dasmOpImm5S (dest, config, line); break;
+        case DASM_IMM5U : dasmOpImm5U (dest, config, line); break;
         case DASM_IMM16S: dasmOpImm16S(dest, config, line); break;
         case DASM_IMM16U: dasmOpImm16U(dest, config, line); break;
         case DASM_JMP   : dasmOpJMP   (dest, config, line); break;
@@ -507,11 +509,13 @@ static int dasmLine(VB *sim, uint32_t *address, uint32_t pc,
     /* Process non-text members */
     line = &(*lines)[index];
     line->address    = *address;
-    line->codeLength = dasmInstSize(sim, *address);
+    line->codeLength = vbuCodeSize(sim, *address);
     line->isPC       = *address == pc;
     for (x = 0; x < line->codeLength; x++)
         line->code[x] = vbRead(sim, *address + x, VB_U8);
-    *address += pc - *address < line->codeLength ?
+
+    /* Advance to the next instruction or PC, whichever is sooner */
+    *address += pc != *address && pc - *address < line->codeLength ?
         pc - *address : line->codeLength;
 
     /* Do not process text members */
@@ -652,10 +656,12 @@ static VBU_DasmLine* dasmDisassemble(VB *sim, uint32_t address,
         }
 
         /* Check if the instruction contains the reference address */
-        size = dasmInstSize(sim, addr);
+        size = vbuCodeSize(sim, addr);
         if (address - addr < size)
             break;
-        addr += pc - addr < size ? pc - addr : size;
+
+        /* Advance to the next instruction or PC, whichever is sooner */
+        addr += addr != pc && pc - addr < size ? pc - addr : size;
     }
 
     /* Address of first line is in the circular buffer */
@@ -666,7 +672,7 @@ static VBU_DasmLine* dasmDisassemble(VB *sim, uint32_t address,
 
     /* Keep decoding until the first line of output */
     else for (; line < 0; line++)
-        addr += dasmInstSize(sim, addr);
+        addr += vbuCodeSize(sim, addr);
 
     /* Working variables */
     size   = length * sizeof (VBU_DasmLine);
@@ -680,7 +686,7 @@ static VBU_DasmLine* dasmDisassemble(VB *sim, uint32_t address,
         if (dasmLine(sim, &addr, pc, config, &lines, &size, &offset, x))
             goto catch;
     }
-    return lines;
+    return VBU_REALLOC(lines, offset);
 
     /* Exception handler */
     catch:

util/vbu.c

@@ -38,6 +38,12 @@ static int32_t SignExtend(int32_t value, int32_t bits) {
 
 /******************************* API Commands ********************************/
 
+/* Determine the size in bytes of an instruction */
+VBUAPI int vbuCodeSize(VB *sim, uint32_t address) {
+    int opcode = vbRead(sim, address, VB_U16) >> 10 & 63;
+    return opcode < 0x20 || opcode == 0x32 || opcode == 0x36 ? 2 : 4;
+}
+
 /* Initialize disassembler options with default settings */
 VBUAPI VBU_DasmConfig* vbuDasmInit(VBU_DasmConfig *config) {
     config->bcondNotation     = VBU_JOINED;
@@ -47,6 +53,7 @@ VBUAPI VBU_DasmConfig* vbuDasmInit(VBU_DasmConfig *config) {
     config->conditionNotation = VBU_NAMES;
     config->hexCase           = VBU_UPPER;
     config->hexNotation       = VBU_0X;
+    config->immediateNotation = VBU_NONE;
     config->memoryNotation    = VBU_OUTSIDE;
     config->mnemonicCase      = VBU_UPPER;
     config->operandOrder      = VBU_DEST_LAST;

util/vbu.h

@@ -29,6 +29,8 @@ extern "C" {
 #define VBU_L          0
 #define VBU_LOWER      1
 #define VBU_NAMES      1
+#define VBU_NONE       0
+#define VBU_NUMBER     1
 #define VBU_NUMBERS    0
 #define VBU_OUTSIDE    0
 #define VBU_SPLIT      1
@@ -48,6 +50,7 @@ typedef struct {               /* Defaults listed first */
     uint8_t conditionNotation; /* NAMES, NUMBERS */
     uint8_t hexCase;           /* UPPER, LOWER */
     uint8_t hexNotation;       /* 0X, H, DOLLAR */
+    uint8_t immediateNotation; /* NONE, NUMBER */
     uint8_t memoryNotation;    /* OUTSIDE, INSIDE */
     uint8_t mnemonicCase;      /* UPPER, LOWER */
     uint8_t operandOrder;      /* DEST_LAST, DEST_FIRST */
@@ -82,6 +85,7 @@ typedef struct {
 
 /******************************* API Commands ********************************/
 
+VBUAPI int             vbuCodeSize   (VB *sim, uint32_t address);
 VBUAPI VBU_DasmConfig* vbuDasmInit   (VBU_DasmConfig *config);
 VBUAPI VBU_DasmLine*   vbuDisassemble(VB *sim, uint32_t address, VBU_DasmConfig *config, unsigned length, int line);
 

web/Audio.js

@@ -0,0 +1,101 @@
+"use strict";
+
+//////////////////////////////////// Audio ////////////////////////////////////
+
+// Dedicated audio output processor
+class Audio extends AudioWorkletProcessor {
+
+    // Instance fields
+    buffers; // Input sample buffer queue
+    core;    // Communications with core thread
+    dom;     // Communications with DOM thread
+    offset;  // Offset into oldest buffer
+
+
+
+    ///////////////////////// Initialization Methods //////////////////////////
+
+    constructor() {
+        super();
+        this.port.onmessage = async e=>{
+            await this.#construct(e.data.core);
+            this.port.postMessage(0);
+        };
+    }
+
+    // Asynchronous constructor
+    async #construct(core) {
+
+        // Configure instance fields
+        this.buffers = [];
+        this.core    = core;
+        this.dom     = this.port;
+        this.offset  = 0;
+
+        // Configure communications
+        this.core.onmessage = e=>this.#onCore(e.data);
+        this.dom .onmessage = e=>this.#onDOM (e.data);
+    }
+
+
+
+    ///////////////////////////// Public Methods //////////////////////////////
+
+    // Produce output samples (called by the user agent)
+    process(inputs, outputs, parameters) {
+        let output = outputs[0];
+        let length = output [0].length;
+        let empty  = null;
+
+        // Process all samples
+        for (let x = 0; x < length;) {
+
+            // No bufferfed samples are available
+            if (this.buffers.length == 0) {
+                for (; x < length; x++)
+                    output[0][x] = output[1][x] = 0;
+                break;
+            }
+
+            // Transfer samples from the oldest buffer
+            let buffer = this.buffers[0];
+            let y      = this.offset;
+            for (; x < length && y < buffer.length; x++, y+=2) {
+                output[0][x] = buffer[y    ];
+                output[1][x] = buffer[y + 1];
+            }
+
+            // Advance to the next buffer
+            if (y == buffer.length) {
+                if (empty == null)
+                    empty = [];
+                empty.push(this.buffers.shift().buffer);
+                this.offset = 0;
+            }
+
+            // Buffer is not empty
+            else this.offset = y;
+        }
+
+        // Return emptied sample buffers to the core thread
+        if (empty != null)
+            this.core.postMessage(empty, empty);
+
+        return true;
+    }
+
+
+
+    ///////////////////////////// Event Handlers //////////////////////////////
+
+    // Message received from core thread
+    #onCore(e) {
+        this.buffers.push(new Float32Array(e));
+    }
+
+    // Message received from DOM thread
+    #onDOM(e) {
+    }
+
+}
+registerProcessor("shrooms-vb", Audio);

web/Constants.js

@@ -0,0 +1,89 @@
+let Constants = {
+
+    // Core
+    VB: {
+
+        // System registers
+        ADTRE: 25,
+        CHCW : 24,
+        ECR  :  4,
+        EIPC :  0,
+        EIPSW:  1,
+        FEPC :  2,
+        FEPSW:  3,
+        PIR  :  6,
+        PSW  :  5,
+        TKCW :  7,
+
+        // Memory access data types
+        S8 : 0,
+        U8 : 1,
+        S16: 2,
+        U16: 3,
+        S32: 4,
+        F32: 5,
+
+        // Option keys
+        PSEUDO_HALT: 0,
+
+        // Controller buttons
+        PWR: 0x0001,
+        SGN: 0x0002,
+        A  : 0x0004,
+        B  : 0x0008,
+        RT : 0x0010,
+        LT : 0x0020,
+        RU : 0x0040,
+        RR : 0x0080,
+        LR : 0x0100,
+        LL : 0x0200,
+        LD : 0x0400,
+        LU : 0x0800,
+        STA: 0x1000,
+        SEL: 0x2000,
+        RL : 0x4000,
+        RD : 0x8000
+    },
+
+    // Utility
+    VBU: {
+
+        // Disassembler options
+        "0X"      : 0,
+        C         : 1,
+        DEST_FIRST: 1,
+        DEST_LAST : 0,
+        DOLLAR    : 1,
+        E         : 0,
+        H         : 2,
+        INSIDE    : 1,
+        JOINED    : 0,
+        L         : 0,
+        LOWER     : 1,
+        NAMES     : 1,
+        NONE      : 0,
+        NUMBER    : 1,
+        NUMBERS   : 0,
+        OUTSIDE   : 0,
+        SPLIT     : 1,
+        UPPER     : 0,
+        Z         : 1
+    },
+
+    // Web interface
+    web: {
+
+        // Break types
+        BREAK_FRAME: 1,
+        BREAK_POINT: 2,
+
+        // Anaglyph colors
+        STEREO_CYAN   : 0x00C6F0,
+        STEREO_GREEN  : 0x00B400,
+        STEREO_MAGENTA: 0xC800FF,
+        STEREO_RED    : 0xFF0000
+    }
+
+};
+
+export { Constants };

web/Core.js

@@ -0,0 +1,570 @@
+"use strict";
+import { Constants } from "./Constants.js";
+
+
+
+//////////////////////////////////// Core /////////////////////////////////////
+
+// Emulation processor
+new class Core {
+
+    // Instance fields
+    audio;       // Audio communication
+    automatic;   // Automatic emulation state
+    clocked;     // Clocked emulation state
+    dom;         // DOM communication
+    mallocs;     // Memory allocations by pointer
+    pointerType; // TypedArray for WebAssembly pointers
+    sims;        // Simulations by pointer
+
+
+
+    ///////////////////////// Initialization Methods //////////////////////////
+
+    constructor() {
+        onmessage = async e=>{
+            await this.#construct(e.data.audio, e.data.wasmUrl);
+            this.dom.postMessage(0);
+        };
+    }
+
+    // Asynchronous constructor
+    async #construct(audio, wasmUrl) {
+
+        // Configure instance fields
+        this.mallocs = new Map();
+        this.sims    = new Map();
+
+        // DOM thread communication
+        this.dom = globalThis;
+        this.dom.onmessage = e=>this[e.data.command](e.data);
+
+        // Instantiate the WebAssembly module
+        this.wasm = (await WebAssembly.instantiateStreaming(
+            fetch(wasmUrl), {
+            env: {
+                emscripten_notify_memory_growth: ()=>this.#onGrowth()
+            }
+        }));
+        Object.assign(this, this.wasm.instance.exports);
+        this.pointerType = this.PointerSize() == 8 ?
+            BigUint64Array : Uint32Array;
+
+        // Configure audio state
+        this.audio = audio;
+        audio.buffers = [0,0,0].map(v=>new Float32Array(41700 / 50 * 2));
+        audio.samples =
+            this.#malloc(41700 / 50 * 2, audio, "samples", Float32Array);
+        audio.onmessage = e=>this.#onAudio(e.data);
+
+        // Configure emulation states
+        this.automatic = { emulating: false };
+        this.clocked   = {};
+        for (let s of [ this.automatic, this.clocked ]) {
+            s.clocks   = this.#malloc(1, s, "clocks"  , Uint32Array);
+            s.pointers = this.#malloc(1, s, "pointers", this.pointerType);
+            s.sims     = [];
+        }
+
+    }
+
+
+
+    ////////////////////////////// Core Commands //////////////////////////////
+
+    // Instantiate sims
+    createSims(message) {
+        let sims = new Array(message.count);
+        let size = this.vbSizeOf();
+
+        // Process all sims
+        for (let x = 0; x < message.count; x++) {
+            let sim = {
+                canvas  : null,
+                keys    : Constants.VB.SGN,
+                pointer : sims[x] = this.CreateSim()
+            };
+            this.sims.set(sim.pointer, sim);
+
+            // Video
+            sim.pixels = this.#getPixels(sim);
+            sim.image  = new ImageData(sim.pixels, 384, 224);
+
+            // Audio
+            sim.samples = this.#noalloc(
+                this.GetExtSamples(sim.pointer),
+                41700 / 50 * 2, sim, "samples", Float32Array
+            );
+
+        }
+
+        this.dom.postMessage({
+            sims    : sims,
+            promised: true
+        });
+    }
+
+    // Produce disassembly from a sim
+    disassemble(message) {
+
+        // Disassemble from the simulation
+        let dasm = message.config == null ?
+            this.vbuDisassemble(
+                message.sim,
+                message.address,
+                0,
+                message.length,
+                message.line
+            )
+        :
+            this.Disassemble(
+                message.config.bcondNotation,
+                message.config.conditionCase,
+                message.config.conditionCL,
+                message.config.conditionEZ,
+                message.config.conditionNotation,
+                message.config.hexCase,
+                message.config.hexNotation,
+                message.config.immediateNotation,
+                message.config.memoryNotation,
+                message.config.mnemonicCase,
+                message.config.operandOrder,
+                message.config.programCase,
+                message.config.programNotation,
+                message.config.setfNotation,
+                message.config.systemCase,
+                message.config.systemNotation,
+                message.sim,
+                message.address,
+                message.length,
+                message.line
+            )
+        ;
+
+        // A memory error occurred
+        if (dasm == 0) {
+            this.dom.postMessage({
+                promised: message.promised,
+                success : false
+            });
+            return;
+        }
+
+        // Retrieve all disassembly data into a working buffer
+        let pointer = this.Realloc(0, message.length * 17 * 4);
+        let buffer  = new Uint32Array(
+            this.memory.buffer, pointer, message.length * 17);
+        this.GetDasm(pointer, dasm, message.length);
+
+        // Consume output lines
+        let lines = new Array(message.length);
+        for (let x = 0, z = 0; x < lines.length; x++) {
+            let line = lines[x] = { text: {} };
+            line.address      = buffer[z++];
+            line.code         = new Array(buffer[z++]);
+            for (let y = 0; y < line.code.length; y++)
+                line.code[y]  = buffer[z++];
+            z += 4 - line.code.length;
+            line.isPC         = buffer[z++] != 0;
+            line.text.address = this.#string(dasm + buffer[z++], true);
+            line.text.code    = new Array(line.code.length);
+            for (let y = 0; y < line.code.length; y++)
+                line.text.code[y] = this.#string(dasm + buffer[z++], true);
+            z += 4 - line.code.length;
+            line.text.mnemonic = this.#string(dasm + buffer[z++], true);
+            line.text.operands = new Array(buffer[z++]);
+            for (let y = 0; y < line.text.operands.length; y++)
+                line.text.operands[y] = this.#string(dasm + buffer[z++], true);
+            z += 3 - line.text.operands.length;
+        }
+
+        // Memory cleanup
+        this.Realloc(pointer, 0);
+        this.Realloc(dasm   , 0);
+
+        // Send response
+        this.dom.postMessage({
+            success : true,
+            lines   : lines,
+            promised: message.promised
+        });
+    }
+
+    // Emulate automatically
+    emulateAutomatic(message) {
+
+        // Configure sims
+        this.automatic.pointers = this.#realloc(
+            this.automatic.pointers, message.sims.length);
+        for (let x = 0; x < message.sims.length; x++) {
+            this.automatic.pointers[x] = message.sims[x];
+            this.automatic.sims    [x] = this.sims.get(message.sims[x]);
+        }
+
+        // Notify the DOM thread
+        this.dom.postMessage({ promised: true });
+
+        // Begin automatic emulation
+        this.automatic.emulating = true;
+        this.#autoEmulate();
+    }
+
+    // Emulate for a given number of clocks
+    emulateClocked(message) {
+
+        // Configure sims
+        this.clocked.pointers = this.#realloc(
+            this.clocked.pointers, message.sims.length);
+        for (let x = 0; x < message.sims.length; x++) {
+            this.clocked.pointers[x] = message.sims[x];
+            this.clocked.sims    [x] = this.sims.get(message.sims[x]);
+        }
+
+        // Process simulations
+        let broke = false;
+        this.clocked.clocks[0] = message.clocks;
+        while (!broke && this.clocked.clocks[0] != 0) {
+
+            // Process simulations until a suspension
+            this.Emulate(
+                this.clocked.pointers.pointer,
+                message.sims.length,
+                this.clocked.clocks.pointer
+            );
+
+            // Monitor break conditions
+            for (let x = 0; x < message.sims.length; x++) {
+                let sim    = this.clocked.sims[x];
+                sim.breaks = this.GetBreaks(sim.pointer);
+                if (breaks & Constants.web.BREAK_POINT)
+                    broke = true;
+            }
+
+        }
+
+        // Update images
+        for (let sim of this.clocked.sims) {
+            if (!(sim.breaks & Constants.web.BREAK_FRAME))
+                continue;
+            this.GetPixels(sim.pointer);
+            sim.context.putImageData(sim.image, 0, 0);
+        }
+
+        // Notify DOM thread
+        this.dom.postMessage({
+            promised: true,
+            broke   : broke,
+            clocks  : this.clocked.clocks[0]
+        });
+    }
+
+    // Specify anaglyph colors
+    setAnaglyph(message) {
+        this.SetAnaglyph(message.sim, message.left, message.right);
+        this.dom.postMessage({ promised: true });
+    }
+
+    // Specify the OffscreenCanvas that goes with a sim
+    setCanvas(message) {
+        let sim = this.sims.get(message.sim);
+        sim.canvas  = message.canvas;
+        sim.context = sim.canvas.getContext("2d");
+        sim.context.putImageData(sim.image, 0, 0);
+        this.dom.postMessage({ promised: true });
+    }
+
+    // Specify a game pak RAM buffer
+    setCartRAM(message) {
+        this.#setCartMemory(message.sim, message.data,
+            this.vbGetCartRAM, this.vbSetCartRAM);
+    }
+
+    // Specify a game pak ROM buffer
+    setCartROM(message) {
+        this.#setCartMemory(message.sim, message.data,
+            this.vbGetCartROM, this.vbSetCartROM);
+    }
+
+    // Specify new game pad keys
+    setKeys(message) {
+        this.vbSetKeys(message.sim, message.keys);
+        this.dom.postMessage({ promised: true });
+    }
+
+    // Specify audio panning
+    setPanning(message) {
+        this.SetPanning(message.sim, message.panning);
+        this.dom.postMessage({ promised: true });
+    }
+
+    // Specify a new communication peer
+    setPeer(message) {
+        let orphaned = [];
+        let prev     = this.vbGetPeer(message.sim);
+        if (prev != message.peer) {
+            if (prev != 0) // Sim's previous peer has been orphaned
+                orphaned.push(prev);
+            if (message.peer != 0) {
+                prev = this.vbGetPeer(message.peer);
+                if (prev != null) // Peer's previous peer has been orphaned
+                    orphaned.push(prev);
+            }
+            this.vbSetPeer(message.sim, message.peer);
+        }
+        this.dom.postMessage({
+            orphaned: orphaned,
+            promised: true
+        });
+    }
+
+    // Specify audio volume
+    setVolume(message) {
+        this.SetVolume(message.sim, message.volume);
+        this.dom.postMessage({ promised: true });
+    }
+
+    // Suspend automatic emulation
+    suspend(message) {
+        this.automatic.emulating = false;
+        this.dom.postMessage({ promised: true });
+    }
+
+
+
+    ///////////////////////////// Event Handlers //////////////////////////////
+
+    // Message from audio thread
+    #onAudio(e) {
+
+        // Output staged images
+        if (this.automatic.emulating && this.audio.buffers.length == 0) {
+            for (let sim of this.automatic.sims)
+                sim.context.putImageData(sim.image, 0, 0);
+        }
+
+        // Acquire the emptied buffers and resume emulation
+        this.audio.buffers.push(... e.map(b=>new Float32Array(b)));
+        this.#autoEmulate();
+    }
+
+    // WebAssembly memory has grown
+    #onGrowth() {
+        for (let prev of this.mallocs.values()) {
+            let buffer = new prev.constructor(
+                this.memory.buffer, prev.pointer, prev.size);
+            Object.assign(buffer, {
+                assign : prev.assign,
+                pointer: prev.pointer,
+                size   : prev.size,
+                target : prev.target
+            });
+            this.mallocs.set(buffer.pointer, buffer);
+            this.#updateTarget(buffer);
+        }
+        for (let sim of this.sims.values()) {
+            sim.pixels = this.#getPixels(sim);
+            sim.image  = new ImageData(sim.pixels, 384, 224);
+        }
+    }
+
+
+
+    ///////////////////////////// Private Methods /////////////////////////////
+
+    // Automatic emulation processing
+    #autoEmulate() {
+
+        // Error checking
+        if (!this.automatic.emulating)
+            return;
+
+        // Process all remaining audio buffers
+        while (this.audio.buffers.length != 0) {
+
+            // Reset sample output
+            for (let sim of this.automatic.sims) {
+                this.vbSetSamples(sim.pointer, sim.samples.pointer,
+                    Constants.VB.F32, 41700 / 50);
+            }
+
+            // Process all clocks
+            this.automatic.clocks[0] = 400000; // 0.02s
+            while (this.automatic.clocks[0] != 0) {
+                this.Emulate(
+                    this.automatic.pointers.pointer,
+                    this.automatic.sims.length,
+                    this.automatic.clocks.pointer
+                );
+
+                // Too many buffers left to output video
+                if (this.audio.buffers.length > 2)
+                    continue;
+
+                // Stage the next video image
+                for (let sim of this.automatic.sims) {
+                    let breaks = this.GetBreaks(sim.pointer);
+                    if (breaks & Constants.web.BREAK_FRAME)
+                        this.GetPixels(sim.pointer);
+                }
+
+            }
+
+            // Mix and output audio samples
+            let buffer = this.audio.buffers.shift();
+            this.Mix(
+                this.audio.samples.pointer,
+                this.automatic.pointers.pointer,
+                this.automatic.sims.length
+            );
+            for (let x = 0; x < buffer.length; x++)
+                buffer[x] = this.audio.samples[x];
+            this.audio.postMessage(buffer.buffer, [ buffer.buffer ]);
+
+            // Output staged images if there's one audio buffer to go
+            if (this.audio.buffers.length != 1)
+                continue;
+            for (let sim of this.automatic.sims)
+                sim.context.putImageData(sim.image, 0, 0);
+        }
+
+    }
+
+    // Delete an allocated buffer in WebAssembly memory
+    #free(buffer) {
+        this.mallocs.delete(buffer.pointer);
+        this.Realloc(buffer.pointer, 0);
+    }
+
+    // Register a sim's pixel buffer
+    #getPixels(sim) {
+        return this.#noalloc(
+            this.GetExtPixels(sim.pointer),
+            384*224*4, sim, "pixels", Uint8ClampedArray
+        );
+    }
+
+    // Allocate memory in WebAssembly and register the buffer
+    #malloc(count, target = null, assign = null, type = Uint8ClampedArray) {
+        return this.#noalloc(
+            this.Realloc(0, count * type.BYTES_PER_ELEMENT),
+            count, target, assign, type
+        );
+    }
+
+    // Register a buffer in WebAssembly memory without allocating it
+    #noalloc(pointer, count, target=null, assign=null, type=Uint8ClampedArray){
+        let buffer = new type(this.memory.buffer, pointer, count);
+        Object.assign(buffer, {
+            assign : assign?.split("."),
+            count  : count,
+            pointer: pointer,
+            target : target
+        });
+        this.mallocs.set(pointer, buffer);
+        return buffer;
+    }
+
+    // Resize a previously allocated buffer in WebAssembly memory
+    #realloc(prev, count) {
+        this.mallocs.delete(prev.pointer);
+        let pointer = this.Realloc(prev.pointer,
+            count * prev.constructor.prototype.BYTES_PER_ELEMENT);
+        let buffer  = new prev.constructor(this.memory.buffer, pointer, count);
+        Object.assign(buffer, {
+            assign : prev.assign,
+            count  : count,
+            pointer: pointer,
+            target : prev.target
+        });
+        this.mallocs.set(pointer, buffer);
+        this.#updateTarget(buffer);
+        return buffer;
+    }
+
+    // Compute anaglyph color values
+    #setAnaglyph(sim, left, right) {
+
+        // Split out the RGB channels
+        let color  = left | right;
+        let stereo = [
+            color >> 16 & 0xFF,
+            color >>  8 & 0xFF,
+            color       & 0xFF
+        ];
+
+        // Compute scaled RGB values by output level
+        sim.anaglyph = new Array(256);
+        for (let x = 0; x < 256; x++) {
+            let level = sim.anaglyph[x] = new Array(3);
+            for (let y = 0; y < 3; y++)
+                level[y] = Math.round(x * stereo[y] / 255.0);
+        }
+
+        // Determine which channels are in each eye
+        sim.anaglyph.left  = [];
+        sim.anaglyph.right = [];
+        for (let x = 0, y = 16; x < 3; x++, y -= 8) {
+            if (left  >> y & 0xFF)
+                sim.anaglyph.left .push(x);
+            if (right >> y & 0xFF)
+                sim.anaglyph.right.push(x);
+        }
+
+    }
+
+    // Specify a game pak memory buffer
+    #setCartMemory(sim, mem, getter, setter) {
+
+        // Working variables
+        let cart = new Uint8Array(mem);
+        let prev = getter(sim);
+        let cur  = this.Realloc(0, cart.length);
+            mem  = new Uint8Array(this.memory.buffer, cur, cart.length);
+
+        // Transfer the data into core memory
+        for (let x = 0; x < mem.length; x++)
+            mem[x] = cart[x];
+
+        // Assign the ROM to the simulation
+        let success = setter(sim, cur, mem.length) == 0;
+        if (success) {
+            if (prev != 0)
+                this.Realloc(prev, 0);
+        } else this.Realloc(cur, 0);
+
+        // Reply to the DOM thread
+        this.dom.postMessage({
+            success : success,
+            promised: true
+        });
+    }
+
+    // Read a C string from WebAssembly memory
+    #string(address, indirect = false) {
+        if (address == 0)
+            return null;
+
+        if (indirect) {
+            let next = new this.pointerType(this.memory.buffer, address, 1)[0];
+            address = next;
+        }
+
+        let length = 0;
+        let memory = new Uint8Array(this.memory.buffer);
+        for (let addr = address; memory[addr++] != 0; length++);
+        return (Array.from(memory.slice(address, address + length))
+            .map(b=>String.fromCodePoint(b)).join(""));
+    }
+
+    // Update an allocated buffer's assignment in its monitor object
+    #updateTarget(buffer) {
+        if (buffer.target == null)
+            return;
+        let obj    = buffer.target;
+        let assign = buffer.assign.slice();
+        while (assign.length > 1)
+            obj = obj[assign.shift()];
+        obj[assign[0]] = buffer;
+    }
+
+}();

web/VB.js

@@ -0,0 +1,935 @@
+"use strict";
+import { Constants } from "./Constants.js";
+
+// Instantiation guard
+const GUARD = Symbol();
+
+
+
+///////////////////////////////// DasmConfig //////////////////////////////////
+
+// Disassembler option settings
+class DasmConfig {
+
+    // Instance fields
+    #bcondNotation;
+    #conditionCase;
+    #conditionCL;
+    #conditionEZ;
+    #conditionNotation;
+    #hexCase;
+    #hexNotation;
+    #immediateNotation;
+    #memoryNotation;
+    #mnemonicCase;
+    #operandOrder;
+    #programCase;
+    #programNotation;
+    #setfNotation;
+    #systemCase;
+    #systemNotation;
+
+
+
+    ///////////////////////// Initialization Methods //////////////////////////
+
+    constructor() {
+        this.#bcondNotation     = Constants.VBU.JOINED;
+        this.#conditionCase     = Constants.VBU.LOWER;
+        this.#conditionCL       = Constants.VBU.L;
+        this.#conditionEZ       = Constants.VBU.Z;
+        this.#conditionNotation = Constants.VBU.NAMES;
+        this.#hexCase           = Constants.VBU.UPPER;
+        this.#hexNotation       = Constants.VBU["0X"];
+        this.#immediateNotation = Constants.VBU.NONE;
+        this.#memoryNotation    = Constants.VBU.OUTSIDE;
+        this.#mnemonicCase      = Constants.VBU.UPPER;
+        this.#operandOrder      = Constants.VBU.DEST_LAST;
+        this.#programCase       = Constants.VBU.LOWER;
+        this.#programNotation   = Constants.VBU.NAMES;
+        this.#setfNotation      = Constants.VBU.SPLIT;
+        this.#systemCase        = Constants.VBU.LOWER;
+        this.#systemNotation    = Constants.VBU.NAMES;
+    }
+
+
+
+    /////////////////////////// Property Accessors ////////////////////////////
+
+    get bcondNotation() { return this.#bcondNotation; }
+    set bcondNotation(value) {
+        switch (value) {
+            case Constants.VBU.JOINED:
+            case Constants.VBU.SPLIT : break;
+            default: return;
+        }
+        this.#bcondNotation = value;
+    }
+
+    get conditionCase() { return this.#conditionCase; }
+    set conditionCase(value) {
+        switch (value) {
+            case Constants.VBU.LOWER:
+            case Constants.VBU.UPPER: break;
+            default: return;
+        }
+        this.#conditionCase = value;
+    }
+
+    get conditionCL() { return this.#conditionCL; }
+    set conditionCL(value) {
+        switch (value) {
+            case Constants.VBU.C:
+            case Constants.VBU.L: break;
+            default: return;
+        }
+        this.#conditionCL = value;
+    }
+
+    get conditionEZ() { return this.#conditionEZ; }
+    set conditionEZ(value) {
+        switch (value) {
+            case Constants.VBU.E:
+            case Constants.VBU.Z: break;
+            default: return;
+        }
+        this.#conditionEZ = value;
+    }
+
+    get conditionNotation() { return this.#conditionNotation; }
+    set conditionNotation(value) {
+        switch (value) {
+            case Constants.VBU.NAMES  :
+            case Constants.VBU.NUMBERS: break;
+            default: return;
+        }
+        this.#conditionNotation = value;
+    }
+
+    get hexCase() { return this.#hexCase; }
+    set hexCase(value) {
+        switch (value) {
+            case Constants.VBU.LOWER:
+            case Constants.VBU.UPPER: break;
+            default: return;
+        }
+        this.#hexCase = value;
+    }
+
+    get hexNotation() { return this.#hexNotation; }
+    set hexNotation(value) {
+        switch (value) {
+            case Constants.VBU["0X"] :
+            case Constants.VBU.DOLLAR:
+            case Constants.VBU.H     : break;
+            default: return;
+        }
+        this.#hexNotation = value;
+    }
+
+    get immediateNotation() { return this.#immediateNotation; }
+    set immediateNotation(value) {
+        switch (value) {
+            case Constants.VBU.NONE  :
+            case Constants.VBU.NUMBER: break;
+            default: return;
+        }
+        this.#immediateNotation = value;
+    }
+
+    get memoryNotation() { return this.#memoryNotation; }
+    set memoryNotation(value) {
+        switch (value) {
+            case Constants.VBU.INSIDE :
+            case Constants.VBU.OUTSIDE: break;
+            default: return;
+        }
+        this.#memoryNotation = value;
+    }
+
+    get mnemonicCase() { return this.#mnemonicCase; }
+    set mnemonicCase(value) {
+        switch (value) {
+            case Constants.VBU.LOWER:
+            case Constants.VBU.UPPER: break;
+            default: return;
+        }
+        this.#mnemonicCase = value;
+    }
+
+    get operandOrder() { return this.#operandOrder; }
+    set operandOrder(value) {
+        switch (value) {
+            case Constants.VBU.DEST_FIRST:
+            case Constants.VBU.DEST_LAST : break;
+            default: return;
+        }
+        this.#operandOrder = value;
+    }
+
+    get programCase() { return this.#programCase; }
+    set programCase(value) {
+        switch (value) {
+            case Constants.VBU.LOWER:
+            case Constants.VBU.UPPER: break;
+            default: return;
+        }
+        this.#programCase = value;
+    }
+
+    get programNotation() { return this.#programNotation; }
+    set programNotation(value) {
+        switch (value) {
+            case Constants.VBU.NAMES  :
+            case Constants.VBU.NUMBERS: break;
+            default: return;
+        }
+        this.#programNotation = value;
+    }
+
+    get setfNotation() { return this.#setfNotation; }
+    set setfNotation(value) {
+        switch (value) {
+            case Constants.VBU.JOINED:
+            case Constants.VBU.SPLIT : break;
+            default: return;
+        }
+        this.#setfNotation = value;
+    }
+
+    get systemCase() { return this.#systemCase; }
+    set systemCase(value) {
+        switch (value) {
+            case Constants.VBU.LOWER:
+            case Constants.VBU.UPPER: break;
+            default: return;
+        }
+        this.#systemCase = value;
+    }
+
+    get systemNotation() { return this.#systemNotation; }
+    set systemNotation(value) {
+        switch (value) {
+            case Constants.VBU.NAMES  :
+            case Constants.VBU.NUMBERS: break;
+            default: return;
+        }
+        this.#systemNotation = value;
+    }
+
+}
+
+
+
+////////////////////////////////// DasmLine ///////////////////////////////////
+
+// One line of disassembler output
+class DasmLine {
+
+    // Instance fields
+    #address;
+    #addressText;
+    #code;
+    #codeText;
+    #isPC;
+    #mnemonicText;
+    #operandText;
+
+
+
+    ///////////////////////// Initialization Methods //////////////////////////
+
+    constructor() {
+        if (arguments[0] != GUARD)
+            throw new Error("Cannot be instantiated.");
+        let line = arguments[1];
+        this.#address      = line.address;
+        this.#addressText  = line.text.address;
+        this.#code         = line.code;
+        this.#codeText     = line.text.code;
+        this.#isPC         = line.isPC;
+        this.#mnemonicText = line.text.mnemonic;
+        this.#operandText  = line.text.operands;
+    }
+
+
+
+    /////////////////////////// Property Accessors ////////////////////////////
+
+    get address() { return this.#address;      }
+    get code   () { return this.#code.slice(); }
+    get isPC   () { return this.#isPC;         }
+    get text   () {
+        return {
+            address : this.#addressText,
+            code    : this.#codeText.slice(),
+            mnemonic: this.#mnemonicText,
+            operands: this.#operandText.slice()
+        };
+    }
+
+
+
+    ///////////////////////////// Public Methods //////////////////////////////
+
+    // Express self as a plain object
+    toObject() {
+        return {
+            address: this.address,
+            code   : Array.from(this.#code),
+            isPC   : this.isPC,
+            text   : this.text
+        };
+    }
+
+}
+
+
+
+///////////////////////////////////// Sim /////////////////////////////////////
+
+// Simulation instance
+class Sim extends HTMLElement {
+
+    // Instance fields
+    #anaglyph;  // Anaglyph color values
+    #canvas;    // Canvas element
+    #core;      // Core proxy
+    #emulating; // Current emulation status
+    #keys;      // Controller state
+    #panning;   // Audio stereo balance
+    #peer;      // Communication peer
+    #pointer;   // Pointer in core memory
+    #volume;    // Audio output volume
+
+
+
+    ///////////////////////// Initialization Methods //////////////////////////
+
+    constructor() {
+        if (arguments[0] != GUARD)
+            throw new Error("Must be created via VB.create()");
+        super();
+        this.proxy = {
+            construct   : (core, pointer)=>this.#construct(core, pointer),
+            isEmulating : ()=>this.#emulating,
+            setEmulating: e =>this.#emulating = e,
+            setPeer     : p =>this.#peer      = p
+        };
+    }
+
+    // Asynchronous constructor
+    async #construct(core, pointer) {
+
+        // Configure instance fields
+        this.#anaglyph  = [ VB.STEREO_RED, VB.STEREO_CYAN ];
+        this.#core      = core;
+        this.#emulating = false;
+        this.#keys      = Constants.VB.SGN;
+        this.#panning   = 0.0;
+        this.#peer      = null;
+        this.#pointer   = pointer;
+        this.#volume    = 1.0;
+        delete this.proxy;
+
+        // Create a <canvas> for the video image
+        let canvas = this.#canvas = document.createElement("canvas");
+        Object.assign(canvas, { width: 384, height: 224 });
+        canvas.style.imageRendering = "pixelated";
+
+        // Configure elements
+        Object.assign(this.style, {
+            display : "inline-block",
+            height  : "224px",
+            position: "relative",
+            width   : "384px"
+        });
+        Object.assign(canvas.style, {
+            height        : "100%",
+            imageRendering: "pixelated",
+            left          : "0",
+            position      : "absolute",
+            top           : "0",
+            width         : "100%"
+        });
+        this.append(canvas);
+
+        // Send control of the canvas to the core worker
+        let offscreen = canvas.transferControlToOffscreen();
+        await core.toCore({
+            command  : "setCanvas",
+            promised : true,
+            sim      : pointer,
+            canvas   : offscreen,
+            transfers: [ offscreen ]
+        });
+
+        return this;
+    }
+
+
+
+    /////////////////////////// Property Accessors ////////////////////////////
+
+    get anaglyph() { return this.#anaglyph.slice(); }
+    get core    () { return this.#core.core       ; }
+    get keys    () { return this.#keys            ; }
+    get panning () { return this.#panning         ; }
+    get peer    () { return this.#peer            ; }
+    get volume  () { return this.#volume          ; }
+
+
+
+    ///////////////////////////// Public Methods //////////////////////////////
+
+    // Delete the sim
+    async delete() {
+        // Unlink peer
+        // Deallocate memory
+        // Unlink core
+    }
+
+    // Disassemble from a simulation
+    async disassemble(address, config, length, line) {
+
+        // Error checking
+        if (!Number.isSafeInteger(address) ||
+            address < 0 || address > 0xFFFFFFFF)
+            throw new RangeError("Address must conform to Uint32.");
+        if (config != null && !(config instanceof DasmConfig))
+            throw new TypeError("Config must be an instance of DasmConfig.");
+        if (!Number.isSafeInteger(address) || length < 0)
+            throw new RangeError("Length must be nonnegative.");
+        if (!Number.isSafeInteger(line))
+            throw new TypeError("Line must be a safe integer.");
+
+        // Request disassembly from the core
+        let response = await this.#core.toCore({
+            command : "disassemble",
+            promised: true,
+            sim     : this.#pointer,
+            address : address,
+            length  : length,
+            line    : line,
+            config  : config == null ? null : {
+                bcondNotation    : config.bcondNotation,
+                conditionCase    : config.conditionCase,
+                conditionCL      : config.conditionCL,
+                conditionEZ      : config.conditionEZ,
+                conditionNotation: config.conditionNotation,
+                hexCase          : config.hexCase,
+                hexNotation      : config.hexNotation,
+                immediateNotation: config.immediateNotation,
+                memoryNotation   : config.memoryNotation,
+                mnemonicCase     : config.mnemonicCase,
+                operandOrder     : config.operandOrder,
+                programCase      : config.programCase,
+                programNotation  : config.programNotation,
+                setfNotation     : config.setfNotation,
+                systemCase       : config.systemCase,
+                systemNotation   : config.systemNotation
+            }
+        });
+
+        // Process the response
+        return !response.success ? null :
+            response.lines.map(l=>new DasmLine(GUARD, l));
+    }
+
+    // Specify anaglyph colors
+    async setAnaglyph(left, right) {
+
+        // Error checking
+        if (!Number.isSafeInteger(left ) || left  < 0 || left  > 0xFFFFFF)
+            throw new RangeError("Left must conform to Uint24.");
+        if (!Number.isSafeInteger(right) || right < 0 || right > 0xFFFFFF)
+            throw new RangeError("Right must conform to Uint24.");
+        if (
+            left & 0xFF0000 && right & 0xFF0000 ||
+            left & 0x00FF00 && right & 0x00FF00 ||
+            left & 0x0000FF && right & 0x0000FF
+        ) throw new RangeError("Left and right overlap RGB channels.");
+
+        // Configure instance fields
+        this.#anaglyph[0] = left;
+        this.#anaglyph[1] = right;
+
+        // Send the colors to the core
+        await this.#core.toCore({
+            command : "setAnaglyph",
+            promised: true,
+            sim     : this.#pointer,
+            left    : left,
+            right   : right
+        });
+    }
+
+    // Specify a game pak RAM buffer
+    setCartRAM(wram) {
+        return this.#setCartMemory("setCartRAM", wram);
+    }
+
+    // Specify a game pak ROM buffer
+    setCartROM(rom) {
+        return this.#setCartMemory("setCartROM", rom);
+    }
+
+    // Specify new game pad keys
+    async setKeys(keys) {
+
+        // Error checking
+        if (!Number.isSafeInteger(keys) || keys < 0 || keys > 0xFFFF)
+            throw new RangeError("Keys must conform to Uint16.");
+        if (keys == this.#keys)
+            return;
+
+        // Configure instance fields
+        this.#keys = keys;
+
+        // Send the keys to the core
+        await this.#core.toCore({
+            command : "setKeys",
+            promised: true,
+            sim     : this.#pointer,
+            keys    : keys
+        });
+    }
+
+    // Specify audio panning
+    async setPanning(panning) {
+
+        // Error checking
+        if (!Number.isFinite(panning) ||panning < -1 || panning > +1) {
+            throw new RangeError(
+                "Panning must be a number from -1 to +1.");
+        }
+
+        // Configure instance fields
+        this.#panning = panning;
+
+        // Send the panning to the core
+        await this.#core.toCore({
+            command : "setPanning",
+            promised: true,
+            sim     : this.#pointer,
+            panning : panning
+        });
+    }
+
+    // Specify a new communication peer
+    async setPeer(peer = null) {
+
+        // Error checking
+        if (peer !== null && peer.#core != this.#core)
+            throw new RangeError("Peer sim must belong to the same core.");
+
+        // Configure peers on the core
+        if (peer != this.#peer)
+            await this.#core.setPeer(this, peer);
+    }
+
+    // Specify audio volume
+    async setVolume(volume) {
+
+        // Error checking
+        if (!Number.isFinite(volume) ||volume < 0 || volume > 10) {
+            throw new RangeError(
+                "Volume must be a number from 0\u00d7 to 10\u00d7.");
+        }
+
+        // Configure instance fields
+        this.#volume = volume;
+
+        // Send the volume to the core
+        await this.#core.toCore({
+            command : "setVolume",
+            promised: true,
+            sim     : this.#pointer,
+            volume  : volume
+        });
+    }
+
+
+
+    ///////////////////////////// Private Methods /////////////////////////////
+
+    // Specify a game pak memory buffer
+    async #setCartMemory(command, mem) {
+
+        // Validation
+        if (mem instanceof ArrayBuffer)
+            mem = new Uint8Array(mem);
+        if (
+            !(mem instanceof Uint8Array) &&
+            !(mem instanceof Uint8ClampedArray)
+        ) mem = Uint8Array.from(mem);
+
+        // Send the memory to the core
+        let response = await this.#core.toCore({
+            command  : command,
+            promised : true,
+            sim      : this.#pointer,
+            data     : mem.buffer,
+            transfers: [ mem.buffer ]
+        });
+        return response.success;
+    }
+
+}
+customElements.define("shrooms-vb", Sim);
+
+
+
+///////////////////////////////////// VB //////////////////////////////////////
+
+// Emulation core interface
+class VB {
+
+    // Static fields
+    static get DasmConfig() { return DasmConfig; }
+    static get DasmLine  () { return DasmLine;   }
+    static get Sim       () { return Sim;        }
+
+    // Instance fields
+    #audio;     // Audio worklet
+    #automatic; // Current automatic emulation group
+    #commands;  // Computed method table
+    #core;      // Core worker
+    #proxy;     // Self proxy for sim access
+    #sims;      // All sims
+    #state;     // Operations state
+
+
+
+    //////////////////////////////// Constants ////////////////////////////////
+
+    // Operations states
+    static #SUSPENDED  = Symbol();
+    static #RESUMING   = Symbol();
+    static #EMULATING  = Symbol();
+    static #SUSPENDING = Symbol();
+
+    // System registers
+    static get ADTRE() { return Constants.VB.ADTRE; }
+    static get CHCW () { return Constants.VB.CHCW ; }
+    static get ECR  () { return Constants.VB.ECR  ; }
+    static get EIPC () { return Constants.VB.EIPC ; }
+    static get EIPSW() { return Constants.VB.EIPSW; }
+    static get FEPC () { return Constants.VB.FEPC ; }
+    static get FEPSW() { return Constants.VB.FEPSW; }
+    static get PIR  () { return Constants.VB.PIR  ; }
+    static get PSW  () { return Constants.VB.PSW  ; }
+    static get TKCW () { return Constants.VB.TKCW ; }
+
+    // Memory access data types
+    static get S8 () { return Constants.VB.S8 ; }
+    static get U8 () { return Constants.VB.U8 ; }
+    static get S16() { return Constants.VB.S16; }
+    static get U16() { return Constants.VB.U16; }
+    static get S32() { return Constants.VB.S32; }
+
+    // Option keys
+    static get PSEUDO_HALT() { return Constants.VB.PSEUDO_HALT; }
+
+    // Controller buttons
+    static get PWR() { return Constants.VB.PWR; }
+    static get SGN() { return Constants.VB.SGN; }
+    static get A  () { return Constants.VB.A  ; }
+    static get B  () { return Constants.VB.B  ; }
+    static get RT () { return Constants.VB.RT ; }
+    static get LT () { return Constants.VB.LT ; }
+    static get RU () { return Constants.VB.RU ; }
+    static get RR () { return Constants.VB.RR ; }
+    static get LR () { return Constants.VB.LR ; }
+    static get LL () { return Constants.VB.LL ; }
+    static get LD () { return Constants.VB.LD ; }
+    static get LU () { return Constants.VB.LU ; }
+    static get STA() { return Constants.VB.STA; }
+    static get SEL() { return Constants.VB.SEL; }
+    static get RL () { return Constants.VB.RL ; }
+    static get RD () { return Constants.VB.RD ; }
+
+    // Disassembler options
+    static get ["0X"]    () { return Constants.VBU["0X"]     ; }
+    static get ABSOLUTE  () { return Constants.VBU.ABSOLUTE  ; }
+    static get C         () { return Constants.VBU.C         ; }
+    static get DEST_FIRST() { return Constants.VBU.DEST_FIRST; }
+    static get DEST_LAST () { return Constants.VBU.DEST_LAST ; }
+    static get DOLLAR    () { return Constants.VBU.DOLLAR    ; }
+    static get E         () { return Constants.VBU.E         ; }
+    static get H         () { return Constants.VBU.H         ; }
+    static get INSIDE    () { return Constants.VBU.INSIDE    ; }
+    static get JOINED    () { return Constants.VBU.JOINED    ; }
+    static get L         () { return Constants.VBU.L         ; }
+    static get LOWER     () { return Constants.VBU.LOWER     ; }
+    static get NAMES     () { return Constants.VBU.NAMES     ; }
+    static get NONE      () { return Constants.VBU.NONE      ; }
+    static get NUMBER    () { return Constants.VBU.NUMBER    ; }
+    static get NUMBERS   () { return Constants.VBU.NUMBERS   ; }
+    static get OUTSIDE   () { return Constants.VBU.OUTSIDE   ; }
+    static get RELATIVE  () { return Constants.VBU.RELATIVE  ; }
+    static get SPLIT     () { return Constants.VBU.SPLIT     ; }
+    static get UPPER     () { return Constants.VBU.UPPER     ; }
+    static get Z         () { return Constants.VBU.Z         ; }
+
+    // Anaglyph colors
+    static get STEREO_CYAN   () { return Constants.web.STEREO_CYAN   ; }
+    static get STEREO_GREEN  () { return Constants.web.STEREO_GREEN  ; }
+    static get STEREO_MAGENTA() { return Constants.web.STEREO_MAGENTA; }
+    static get STEREO_RED    () { return Constants.web.STEREO_RED    ; }
+
+
+
+    ///////////////////////////// Static Methods //////////////////////////////
+
+    // Create a core instance
+    static async create(options) {
+        return await new VB(GUARD).#construct(options);
+    }
+
+
+
+    ///////////////////////// Initialization Methods //////////////////////////
+
+    constructor() {
+        if (arguments[0] != GUARD)
+            throw new Error("Must be created via VB.create()");
+    }
+
+    // Asynchronous constructor
+    async #construct(options) {
+
+        // Configure instance fields
+        this.#automatic = null;
+        this.#sims      = new Map();
+        this.#state     = VB.#SUSPENDED;
+
+        // Ensure default options
+        options          ??= {};
+        options.audioUrl ??= import.meta.resolve("./Audio.js");
+        options.coreUrl  ??= import.meta.resolve("./Core.js");
+        options.wasmUrl  ??= import.meta.resolve("./core.wasm");
+
+        // Core<->audio communications
+        let channel = new MessageChannel();
+
+        // Audio output context
+        let audio = new AudioContext({
+            latencyHint: "interactive",
+            sampleRate : 41700
+        });
+        await audio.suspend();
+
+        // Audio node
+        await audio.audioWorklet.addModule(options.audioUrl);
+        audio = this.#audio = new AudioWorkletNode(audio, "shrooms-vb", {
+            numberOfInputs    :  0,
+            numberOfOutputs   :  1,
+            outputChannelCount: [2]
+        });
+        audio.connect(audio.context.destination);
+
+        // Send one message channel port to the audio worklet
+        await new Promise(resolve=>{
+            audio.port.onmessage = resolve;
+            audio.port.postMessage({
+                core: channel.port1
+            }, [channel.port1]);
+        });
+        audio.port.onmessage = null;//e=>this.#onAudio(e.data);
+
+        // Core worker
+        let core = this.#core = new Worker(options.coreUrl, {type: "module"});
+        core.promises = [];
+
+        // Send the other message channel port to the core worker
+        await new Promise(resolve=>{
+            core.onmessage = resolve;
+            core.postMessage({
+                audio  : channel.port2,
+                wasmUrl: options.wasmUrl
+            }, [ channel.port2 ]);
+        });
+        core.onmessage = e=>this.#onCore(e.data);
+
+        // Establish a concealed proxy for sim objects
+        this.#proxy = {
+            core   : this,
+            setPeer: (a,b)=>this.#setPeer(a,b),
+            toCore : m=>this.#toCore(m)
+        };
+
+        // Configure command table
+        this.#commands = {
+            // Will be used with subscriptions
+        };
+
+        return this;
+    }
+
+
+
+    ///////////////////////////// Public Methods //////////////////////////////
+
+    // Create one or more sims
+    async create(count = null) {
+
+        // Error checking
+        if (count !== null && (!Number.isSafeInteger(count) || count < 1)) {
+            throw new RangeError(
+                "Count must be a safe integer and at least 1.");
+        }
+
+        // Allocate memory in the core
+        let response = await this.#toCore({
+            command : "createSims",
+            promised: true,
+            count   : count ?? 1
+        });
+
+        // Produce Sim elements for each instance
+        let sims = response.sims;
+        for (let x = 0; x < (count ?? 1); x++) {
+            let proxy = new Sim(GUARD).proxy;
+            proxy.pointer = sims[x];
+            proxy.sim     = sims[x] =
+                await proxy.construct(this.#proxy, sims[x]);
+            this.#sims.set(sims[x], proxy);
+            this.#sims.set(proxy.pointer, proxy);
+        }
+        return count === null ? sims[0] : sims;
+    }
+
+    // Begin emulation
+    async emulate(sims, clocks) {
+
+        // Error checking
+        if (sims instanceof Sim)
+            sims = [sims];
+        if (
+            !Array.isArray(sims) ||
+            sims.length == 0     ||
+            sims.find(s=>!this.#sims.has(s))
+        ) {
+            throw new TypeError("Must specify a Sim or array of Sims " +
+                "that belong to this core.");
+        }
+        if (sims.find(s=>this.#sims.get(s).isEmulating()))
+            throw new Error("Sims cannot already be part of emulation.");
+        if (
+            clocks !== true &&
+            !(Number.isSafeInteger(clocks) && clocks >= 0)
+        ) {
+            throw new RangeError(
+                "Clocks must be true or a nonnegative safe integer.");
+        }
+
+        // Cannot resume automatic emulation
+        if (clocks === true && this.#state != VB.#SUSPENDED)
+            return false;
+
+        // Manage sims
+        let proxies  = sims   .map(s=>this.#sims.get(s));
+        let pointers = proxies.map(p=>p.pointer);
+        for (let sim of proxies)
+            sim.setEmulating(true);
+
+        // Clocked emulation
+        if (clocks !== true) {
+            let response = await this.#toCore({
+                command : "emulateClocked",
+                promised: true,
+                sims    : pointers,
+                clocks  : clocks
+            });
+            for (let sim of proxies)
+                sim.setEmulating(false);
+            return {
+                broke : response.broke,
+                clocks: response.clocks
+            };
+        }
+
+        // Resume automatic emulation
+        this.#automatic = proxies;
+        this.#state     = VB.#RESUMING;
+        if (this.#audio.context.state == "suspended")
+            await this.#audio.context.resume();
+        await this.#toCore({
+            command : "emulateAutomatic",
+            promised: true,
+            sims    : pointers
+        });
+        this.#state = VB.#EMULATING;
+        return true;
+    }
+
+    // Suspend automatic emulation
+    async suspend() {
+
+        // Error checking
+        if (this.#state != VB.#EMULATING)
+            return false;
+
+        // Tell the core to stop emulating
+        this.#state = VB.#SUSPENDING;
+        await this.#toCore({
+            command : "suspend",
+            promised: true
+        });
+
+        // Configure state
+        this.#state = VB.#SUSPENDED;
+        for (let sim of this.#automatic)
+            sim.setEmulating(false);
+        return true;
+    }
+
+
+
+    ///////////////////////////// Private Methods /////////////////////////////
+
+    // Message received from core worker
+    #onCore(message) {
+        if (message.promised)
+            this.#core.promises.shift()(message);
+        if ("command" in message)
+            this.#commands[message.command](message);
+    }
+
+    // Specify a new communication peer
+    async #setPeer(sim, peer) {
+
+        // Associate the peers on the core
+        let response = await this.#toCore({
+            command : "setPeer",
+            promised: true,
+            sim     : this.#sims.get(sim).pointer,
+            peer    : peer == null ? 0 : this.#sims.get(peer).pointer
+        });
+
+        // Link sims
+        this.#sims.get(sim).setPeer(peer);
+        if (peer != null)
+            this.#sims.get(peer).setPeer(sim);
+
+        // Unlink orphaned sims
+        for (let pointer of response.orphaned)
+            this.#sims.get(pointer).setPeer(null);
+    }
+
+    // Send a message to the core worker
+    async #toCore(message) {
+        let transfers = message.transfers;
+        if (transfers != null)
+            delete message.transfers;
+        return await new Promise(resolve=>{
+            if (message.promised)
+                this.#core.promises.push(resolve);
+            this.#core.postMessage(message, transfers ?? []);
+        });
+    }
+
+}
+
+export { VB };

web/wasm.c

@@ -0,0 +1,273 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <emscripten/emscripten.h>
+#include <vb.h>
+#include <vbu.h>
+
+
+
+////////////////////////////////// Constants //////////////////////////////////
+
+// Break conditions
+#define BREAK_FRAME 1
+#define BREAK_POINT 2
+
+// Anaglyph colors
+#define STEREO_CYAN    0x00C6F0
+#define STEREO_GREEN   0x00B400
+#define STEREO_MAGENTA 0xC800FF
+#define STEREO_RED     0xFF0000
+
+// Element counts
+#define NUM_SAMPLES (41700 / 50 * 2)
+
+
+
+//////////////////////////////////// Types ////////////////////////////////////
+
+// Additional monitor state for simulations
+typedef struct {
+    int32_t  breaks;
+    uint32_t left[256];
+    float    panning;
+    uint8_t  pixels[384 * 224 * 4];
+    uint32_t right[256];
+    float    samples[NUM_SAMPLES];
+    float    volume;
+} Ext;
+
+
+
+////////////////////////////////// Callbacks //////////////////////////////////
+
+// Frame callback
+int wasmOnFrame(VB *sim) {
+    ((Ext *) vbGetUserData(sim))->breaks |= BREAK_FRAME;
+    return 1;
+}
+
+
+
+/////////////////////////////// Module Exports ////////////////////////////////
+
+// Specify anaglyph colors
+EMSCRIPTEN_KEEPALIVE void SetAnaglyph(VB *sim, uint32_t left, uint32_t right) {
+    Ext *ext = (Ext *) vbGetUserData(sim);
+
+    // Erase all RGB values
+    for (int x = 0; x < 256; x++)
+        ext->left[x] = ext->right[x] = 0xFF000000;
+
+    // Process all RGB channels
+    for (int c = 0, shift = 16; c < 3; c++, shift -= 8) {
+        double    max;  // Magnitude of channel value
+        uint32_t *dest; // Lookup data
+
+        // Select the magnitude and lookup channel
+        dest = ext->left;
+        max  = (left >> shift & 0xFF) / 255.0;
+        if (max == 0) {
+            dest = ext->right;
+            max  = (right >> shift & 0xFF) / 255.0;
+            if (max == 0)
+                continue;
+        }
+
+        // Compute the resulting RGB values
+        for (int x = 0; x < 256; x++)
+            *dest++ |= (uint32_t) (x * max + 0.5) << (16 - shift);
+    }
+
+}
+
+// Instantiate a simulation
+EMSCRIPTEN_KEEPALIVE void* CreateSim() {
+    size_t   sizeOfSim = vbSizeOf();
+    uint8_t *pointer   = malloc(sizeOfSim + sizeof (Ext));
+
+    // Configure sim
+    VB *sim = vbInit((VB *) pointer);
+    vbSetFrameCallback(sim, &wasmOnFrame);
+    vbSetOption(sim, VB_PSEUDO_HALT, 1);
+
+    // Configure extra
+    Ext *ext = (Ext *) (pointer + sizeOfSim);
+    ext->breaks  = 0;
+    ext->panning = 0.0f;
+    ext->volume  = 1.0f;
+    vbSetUserData(sim, ext);
+    SetAnaglyph(sim, STEREO_RED, STEREO_CYAN);
+
+    // Initialize pixels with opaque black
+    for (unsigned x = 0; x < 384 * 224; x++)
+        ((uint32_t *) ext->pixels)[x] = 0xFF000000;
+
+    return sim;
+}
+
+// Disassemble from a simulation
+EMSCRIPTEN_KEEPALIVE void* Disassemble(
+    int bcondNotation, int conditionCase, int conditionCL, int conditionEZ,
+    int conditionNotation, int hexCase, int hexNotation, int immediateNotation,
+    int memoryNotation, int mnemonicCase, int operandOrder, int programCase,
+    int programNotation, int setfNotation, int systemCase, int systemNotation,
+    VB *sim, uint32_t address, unsigned length, int line
+) {
+    VBU_DasmConfig config;
+    config.bcondNotation     = bcondNotation;
+    config.conditionCase     = conditionCase;
+    config.conditionCL       = conditionCL;
+    config.conditionEZ       = conditionEZ;
+    config.conditionNotation = conditionNotation;
+    config.hexCase           = hexCase;
+    config.hexNotation       = hexNotation;
+    config.immediateNotation = immediateNotation;
+    config.memoryNotation    = memoryNotation;
+    config.mnemonicCase      = mnemonicCase;
+    config.operandOrder      = operandOrder;
+    config.programCase       = programCase;
+    config.programNotation   = programNotation;
+    config.setfNotation      = setfNotation;
+    config.systemCase        = systemCase;
+    config.systemNotation    = systemNotation;
+    return vbuDisassemble(sim, address, &config, length, line);
+}
+
+// Process simulations
+EMSCRIPTEN_KEEPALIVE int Emulate(VB **sims, unsigned count, uint32_t *clocks) {
+    for (unsigned x = 0; x < count; x++)
+        ((Ext *) vbGetUserData(sims[x]))->breaks = 0;
+    return vbEmulateEx(sims, count, clocks);
+}
+
+// Retrieve a sim's pixel pointer
+EMSCRIPTEN_KEEPALIVE void* GetExtPixels(VB *sim) {
+    return ((Ext *) vbGetUserData(sim))->pixels;
+}
+
+// Retrieve a sim's sample pointer
+EMSCRIPTEN_KEEPALIVE void* GetExtSamples(VB *sim) {
+    return ((Ext *) vbGetUserData(sim))->samples;
+}
+
+// Retrieve the break condition flags for a sim
+EMSCRIPTEN_KEEPALIVE int32_t GetBreaks(VB *sim) {
+    return ((Ext *) vbGetUserData(sim))->breaks;
+}
+
+// Serialize disassembled lines into a linear buffer
+EMSCRIPTEN_KEEPALIVE void GetDasm(uint32_t *buffer, void *dasm, int count) {
+    for (int x = 0; x < count; x++) {
+        VBU_DasmLine *line = &((VBU_DasmLine *) dasm)[x];
+
+        // Numeric data
+        *buffer++ = line->address;
+        *buffer++ = line->codeLength;
+        for (int y = 0; y < 4; y++)
+            *buffer++ = line->code[y];
+        *buffer++ = line->isPC;
+
+        // Text data -- Store offset of string pointer from start of dasm
+        *buffer++ = (uint32_t) ((void *) &line->text.address - dasm);
+        for (int y = 0; y < 4; y++)
+            *buffer++ = (uint32_t) ((void *) &line->text.code[y] - dasm);
+        *buffer++ = (uint32_t) ((void *) &line->text.mnemonic - dasm);
+        *buffer++ = line->text.operandsLength;
+        for (int y = 0; y < 3; y++)
+            *buffer++ = (uint32_t) ((void *) &line->text.operands[y] - dasm);
+    }
+}
+
+// Retrieve anaglyph-tinted pixels from a sim
+EMSCRIPTEN_KEEPALIVE void GetPixels(VB *sim) {
+    Ext     *ext    = (Ext *) vbGetUserData(sim);
+    uint8_t *pixels = ext->pixels;
+    vbGetPixels(sim, pixels, 4, 384 * 4, pixels + 1, 4, 384 * 4);
+    for (unsigned x = 0; x < 384 * 224 * 4; x += 4, pixels += 4)
+        *(uint32_t *) pixels = ext->left[pixels[0]] | ext->right[pixels[1]];
+}
+
+// Mix audio samples for output
+EMSCRIPTEN_KEEPALIVE void Mix(float *buffer, VB **sims, int count) {
+
+    // Process all sims
+    for (int x = 0; x < count; x++) {
+        Ext   *ext     = (Ext *) vbGetUserData(sims[x]);
+        float *samples = ext->samples;
+        float  v       = ext->volume;
+
+        // First sim initializes buffer
+        if (x == 0) {
+            if (ext->panning < 0) {
+                float l = -ext->panning * v;
+                float r = (1.0f + ext->panning) * v;
+                for (unsigned y = 0; y < NUM_SAMPLES; y += 2) {
+                    buffer[y    ] = samples[y] * v + samples[y + 1] * l;
+                    buffer[y + 1] = samples[y + 1] * r;
+                }
+            } else if (ext->panning > 0) {
+                float r = ext->panning * v;
+                float l = (1.0f - ext->panning) * v;
+                for (unsigned y = 0; y < NUM_SAMPLES; y += 2) {
+                    buffer[y    ] = samples[y] * l;
+                    buffer[y + 1] = samples[y + 1] * v + samples[y] * r;
+                }
+            } else {
+                for (unsigned y = 0; y < NUM_SAMPLES; y++)
+                    buffer[y] = samples[y] * v;
+            }
+        }
+
+        // Subsequent sims add to buffer
+        else {
+            if (ext->panning < 0) {
+                float l = -ext->panning * v;
+                float r = (1.0f + ext->panning) * v;
+                for (unsigned y = 0; y < NUM_SAMPLES; y += 2) {
+                    buffer[y    ] += samples[y] * v + samples[y + 1] * l;
+                    buffer[y + 1] += samples[y + 1] * r;
+                }
+            } else if (ext->panning > 0) {
+                float r = ext->panning * v;
+                float l = (1.0f - ext->panning) * v;
+                for (unsigned y = 0; y < NUM_SAMPLES; y += 2) {
+                    buffer[y    ] += samples[y] * l;
+                    buffer[y + 1] += samples[y + 1] * v + samples[y] * r;
+                }
+            } else {
+                for (unsigned y = 0; y < NUM_SAMPLES; y++)
+                    buffer[y] += samples[y] * v;
+            }
+        }
+
+    }
+
+    // Clipping
+    for (unsigned y = 0; y < NUM_SAMPLES; y++) {
+        if (buffer[y] < -1.0f)
+            buffer[y] = -1.0f;
+        else if (buffer[y] > +1.0f)
+            buffer[y] = +1.0f;
+    }
+
+}
+
+// Determine the size in bytes of a pointer
+EMSCRIPTEN_KEEPALIVE int PointerSize() {
+    return sizeof (void *);
+}
+
+// Memory management
+EMSCRIPTEN_KEEPALIVE void* Realloc(void *data, size_t size) {
+    return realloc(data, size);
+}
+
+// Specify audio panning
+EMSCRIPTEN_KEEPALIVE void SetPanning(VB *sim, float panning) {
+    ((Ext *) vbGetUserData(sim))->panning = panning;
+}
+
+// Specify audio volume
+EMSCRIPTEN_KEEPALIVE void SetVolume(VB *sim, float volume) {
+    ((Ext *) vbGetUserData(sim))->volume = volume;
+}