diff --git a/src/emulator.rs b/src/emulator.rs
index 672e5c9..814149b 100644
--- a/src/emulator.rs
+++ b/src/emulator.rs
@@ -141,6 +141,8 @@ pub struct Emulator {
     linked: Arc<AtomicBool>,
     renderers: HashMap<SimId, TextureSink>,
     messages: HashMap<SimId, mpsc::Sender<Toast>>,
+    eye_contents: Vec<u8>,
+    audio_samples: Vec<f32>,
 }
 
 impl Emulator {
@@ -164,6 +166,8 @@ impl Emulator {
             linked,
             renderers: HashMap::new(),
             messages: HashMap::new(),
+            eye_contents: vec![0u8; 384 * 224 * 2],
+            audio_samples: vec![0.0; EXPECTED_FRAME_SIZE],
         })
     }
 
@@ -257,56 +261,8 @@ impl Emulator {
     }
 
     pub fn run(&mut self) {
-        let mut eye_contents = vec![0u8; 384 * 224 * 2];
-        let mut audio_samples = vec![];
         loop {
-            let p1_running = self.running[SimId::Player1.to_index()].load(Ordering::Acquire);
-            let p2_running = self.running[SimId::Player2.to_index()].load(Ordering::Acquire);
-            let mut idle = p1_running || p2_running;
-            if p1_running && p2_running {
-                Sim::emulate_many(&mut self.sims);
-            } else if p1_running {
-                self.sims[SimId::Player1.to_index()].emulate();
-            } else if p2_running {
-                self.sims[SimId::Player2.to_index()].emulate();
-            }
-
-            for sim_id in SimId::values() {
-                let Some(renderer) = self.renderers.get_mut(&sim_id) else {
-                    continue;
-                };
-                let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
-                    continue;
-                };
-                if sim.read_pixels(&mut eye_contents) {
-                    idle = false;
-                    if renderer.queue_render(&eye_contents).is_err() {
-                        self.renderers.remove(&sim_id);
-                    }
-                }
-            }
-            let p1_audio =
-                p1_running && self.audio_on[SimId::Player1.to_index()].load(Ordering::Acquire);
-            let p2_audio =
-                p2_running && self.audio_on[SimId::Player2.to_index()].load(Ordering::Acquire);
-            let weight = if p1_audio && p2_audio { 0.5 } else { 1.0 };
-            if p1_audio {
-                if let Some(sim) = self.sims.get_mut(SimId::Player1.to_index()) {
-                    sim.read_samples(&mut audio_samples, weight);
-                }
-            }
-            if p2_audio {
-                if let Some(sim) = self.sims.get_mut(SimId::Player2.to_index()) {
-                    sim.read_samples(&mut audio_samples, weight);
-                }
-            }
-            if audio_samples.is_empty() {
-                audio_samples.resize(EXPECTED_FRAME_SIZE, 0.0);
-            } else {
-                idle = false;
-            }
-            self.audio.update(&audio_samples);
-            audio_samples.clear();
+            let idle = self.tick();
             if idle {
                 // The game is paused, and we have output all the video/audio we have.
                 // Block the thread until a new command comes in.
@@ -331,6 +287,58 @@ impl Emulator {
         }
     }
 
+    // returns true if the emulator is "idle" (i.e. this didn't output anything)
+    pub fn tick(&mut self) -> bool {
+        let p1_running = self.running[SimId::Player1.to_index()].load(Ordering::Acquire);
+        let p2_running = self.running[SimId::Player2.to_index()].load(Ordering::Acquire);
+        let mut idle = p1_running || p2_running;
+        if p1_running && p2_running {
+            Sim::emulate_many(&mut self.sims);
+        } else if p1_running {
+            self.sims[SimId::Player1.to_index()].emulate();
+        } else if p2_running {
+            self.sims[SimId::Player2.to_index()].emulate();
+        }
+
+        for sim_id in SimId::values() {
+            let Some(renderer) = self.renderers.get_mut(&sim_id) else {
+                continue;
+            };
+            let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
+                continue;
+            };
+            if sim.read_pixels(&mut self.eye_contents) {
+                idle = false;
+                if renderer.queue_render(&self.eye_contents).is_err() {
+                    self.renderers.remove(&sim_id);
+                }
+            }
+        }
+        let p1_audio =
+            p1_running && self.audio_on[SimId::Player1.to_index()].load(Ordering::Acquire);
+        let p2_audio =
+            p2_running && self.audio_on[SimId::Player2.to_index()].load(Ordering::Acquire);
+        let weight = if p1_audio && p2_audio { 0.5 } else { 1.0 };
+        if p1_audio {
+            if let Some(sim) = self.sims.get_mut(SimId::Player1.to_index()) {
+                sim.read_samples(&mut self.audio_samples, weight);
+            }
+        }
+        if p2_audio {
+            if let Some(sim) = self.sims.get_mut(SimId::Player2.to_index()) {
+                sim.read_samples(&mut self.audio_samples, weight);
+            }
+        }
+        if self.audio_samples.is_empty() {
+            self.audio_samples.resize(EXPECTED_FRAME_SIZE, 0.0);
+        } else {
+            idle = false;
+        }
+        self.audio.update(&self.audio_samples);
+        self.audio_samples.clear();
+        idle
+    }
+
     fn handle_command(&mut self, command: EmulatorCommand) {
         match command {
             EmulatorCommand::ConnectToSim(sim_id, renderer, messages) => {