diff --git a/game.c b/game.c
index c9d9b0a..4f756ee 100644
--- a/game.c
+++ b/game.c
@@ -6,10 +6,16 @@
 
 int sleepNanos(long int ns) {
     struct timespec time;
+    if (ns < 0) return 0;
     time.tv_sec = ns / 1000000000;
     time.tv_nsec = ns % 1000000000;
     return nanosleep(&time, NULL);
 }
+long int tickNs() {
+    struct timespec time;
+    clock_gettime(CLOCK_MONOTONIC, &time);
+    return (time.tv_sec * 1000000000) + time.tv_nsec;
+}
 
 typedef struct {
     GraphicsContext *gfx;
@@ -46,17 +52,17 @@ int runGame(VB *sim, GraphicsContext *gfx) {
     gfxUpdateLeftEye(gfx, LEFT_EYE_DEFAULT);
     gfxUpdateRightEye(gfx, RIGHT_EYE_DEFAULT);
 
-    prevTicks = SDL_GetTicks64();
     while (1) {
         clocks = MAX_STEP_CLOCKS;
+        prevTicks = tickNs();
         vbEmulate(sim, &clocks);
-        ticks = SDL_GetTicks64();
+        ticks = tickNs();
         while (SDL_PollEvent(&event)) {
             if (event.type == SDL_QUIT) {
                 return 0;
             }
         }
-        sleepNanos(((MAX_STEP_CLOCKS - clocks) * 50) - (ticks - prevTicks) * 1000);
+        sleepNanos(((MAX_STEP_CLOCKS - clocks) * 50) - (ticks - prevTicks));
         prevTicks = ticks;
     }
 }