diff --git a/life/assets/audioOff.png b/life/assets/audioOff.png
new file mode 100644
index 0000000..bf3622b
Binary files /dev/null and b/life/assets/audioOff.png differ
diff --git a/life/assets/audioOn.png b/life/assets/audioOn.png
new file mode 100644
index 0000000..65a3194
Binary files /dev/null and b/life/assets/audioOn.png differ
diff --git a/life/src/main.rs b/life/src/main.rs
index 18e733d..ae9d6f6 100644
--- a/life/src/main.rs
+++ b/life/src/main.rs
@@ -22,10 +22,10 @@ fn main() {
         .init_resource::<Coordinates>()
         .init_resource::<CellAssets>()
         .init_resource::<Panning>()
-        .init_state::<SimulationState>()
+        .init_state::<SimulationPlayback>()
+        .init_state::<AudioPlayback>()
         .insert_resource(GlobalVolume::new(Volume::Linear(1.0)))
         .add_message::<Lifecycle>()
-        .add_message::<SimulationState>()
         .add_systems(Startup, setup)
         .add_systems(Startup, load_audio_tones)
         .add_systems(Startup, load_materials)
@@ -36,7 +36,9 @@ fn main() {
         )
         .add_systems(
             Update,
-            modulate_volume, // TODO: .run_if(any_component_added::<AudioSink>)
+            // Run if any component added/removed: AudioSink
+            // Run if state changed: AudioPlayback
+            control_volume,
         )
         .add_systems(Update, grid_gizmo)
         .add_systems(
@@ -57,12 +59,12 @@ fn main() {
         .add_systems(
             Update,
             simulation_step
-                .run_if(in_state(SimulationState::Run))
+                .run_if(in_state(SimulationPlayback::Run))
                 .run_if(cooldown_secs(FRAME_DURATION)),
         )
         .add_systems(
             Update,
-            simulation_step.run_if(on_message::<SimulationState>),
+            simulation_step.run_if(state_changed::<SimulationPlayback>),
         )
         .add_systems(
             Update,
@@ -71,6 +73,14 @@ fn main() {
         .add_systems(Update, cell_lifecycle.run_if(on_message::<Lifecycle>))
         .add_systems(Update, mouse_pan.run_if(on_message::<MouseMotion>))
         .add_systems(Update, set_pan_state)
+        .add_systems(
+            Update,
+            toggle_state_entities::<SimulationPlayback>.run_if(state_changed::<SimulationPlayback>),
+        )
+        .add_systems(
+            Update,
+            toggle_state_entities::<AudioPlayback>.run_if(state_changed::<AudioPlayback>),
+        )
         .add_observer(on_add_ui_button)
         .add_observer(on_add_coordinates)
         .run();
@@ -78,6 +88,13 @@ fn main() {
 
 const SCALE: f32 = 100.0;
 
+#[derive(States, Debug, Default, Hash, PartialEq, Eq, Clone, Component)]
+enum AudioPlayback {
+    #[default]
+    Mute,
+    Play,
+}
+
 #[derive(Debug, Component, PartialEq)]
 #[require(Visibility, Transform)]
 enum UiButton {
@@ -87,6 +104,8 @@ enum UiButton {
     Play,
     ZoomOut,
     ZoomIn,
+    PlayAudio,
+    MuteAudio,
 }
 
 impl UiButton {
@@ -98,6 +117,8 @@ impl UiButton {
             Self::Play => "forward.png",
             Self::ZoomOut => "zoomOut.png",
             Self::ZoomIn => "zoomIn.png",
+            Self::PlayAudio => "audioOn.png",
+            Self::MuteAudio => "audioOff.png",
         }
     }
 }
@@ -171,32 +192,38 @@ fn setup(mut commands: Commands) {
         ))
         .with_children(|parent| {
             parent.spawn(UiButton::Power).observe(shutdown);
-            // TODO: Play/Pause Toggle
-            parent.spawn(UiButton::Pause).observe(pause_sim);
-            parent.spawn(UiButton::Play).observe(play_sim);
+            // TODO: Reset button
+            parent
+                .spawn((UiButton::Pause, SimulationPlayback::Run))
+                .observe(pause_sim);
+            parent
+                .spawn((UiButton::Play, SimulationPlayback::Pause))
+                .observe(play_sim);
             parent.spawn(UiButton::Step).observe(step_sim);
             parent.spawn(UiButton::ZoomOut).observe(zoom_out);
             parent.spawn(UiButton::ZoomIn).observe(zoom_in);
-            // TODO: Reset button
             // TODO: Mute/Unmute Toggle
+            parent
+                .spawn((UiButton::MuteAudio, AudioPlayback::Play))
+                .observe(mute_audio);
+            parent
+                .spawn((UiButton::PlayAudio, AudioPlayback::Mute))
+                .observe(play_audio);
         });
 
     fn shutdown(_trigger: On<Pointer<Press>>, mut writer: MessageWriter<AppExit>) {
         writer.write(AppExit::Success);
     }
-    fn pause_sim(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<SimulationState>>) {
-        next.set(SimulationState::Pause);
+    fn play_sim(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<SimulationPlayback>>) {
+        // Set simulation state
+        next.set(SimulationPlayback::Run);
     }
-    fn step_sim(
-        _trigger: On<Pointer<Press>>,
-        mut writer: MessageWriter<SimulationState>,
-        mut next: ResMut<NextState<SimulationState>>,
-    ) {
-        next.set(SimulationState::Step);
-        writer.write(SimulationState::Step);
+    fn pause_sim(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<SimulationPlayback>>) {
+        // Set simulation state
+        next.set(SimulationPlayback::Pause);
     }
-    fn play_sim(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<SimulationState>>) {
-        next.set(SimulationState::Run);
+    fn step_sim(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<SimulationPlayback>>) {
+        next.set(SimulationPlayback::Step);
     }
     fn zoom_out(_trigger: On<Pointer<Press>>, mut projection: Query<&mut Projection>) {
         projection.iter_mut().for_each(|mut p| match *p {
@@ -214,6 +241,12 @@ fn setup(mut commands: Commands) {
             _ => todo!(),
         });
     }
+    fn play_audio(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<AudioPlayback>>) {
+        next.set(AudioPlayback::Play);
+    }
+    fn mute_audio(_trigger: On<Pointer<Press>>, mut next: ResMut<NextState<AudioPlayback>>) {
+        next.set(AudioPlayback::Mute);
+    }
 }
 
 #[derive(Debug, Default, Clone, PartialEq, Hash, Eq, Component, Resource)]
@@ -398,8 +431,8 @@ fn assert_cell_uniqueness(q: Query<(Entity, &Coordinates), With<Cell>>) {
     })
 }
 
-#[derive(States, Debug, Default, Hash, PartialEq, Eq, Clone, Message)]
-enum SimulationState {
+#[derive(States, Debug, Default, Hash, PartialEq, Eq, Clone, Component)]
+enum SimulationPlayback {
     #[default]
     Pause,
     Run,
@@ -532,13 +565,13 @@ fn cooldown_secs(input: f32) -> impl FnMut(Local<Timer>, Res<Time>) -> bool + Cl
 //   If in Pause state, keep Pauses button light, or blinking or outlined or something.
 fn visualize_ui_state(
     mut query: Query<(&UiButton, &mut Outline)>,
-    state: Res<State<SimulationState>>,
+    state: Res<State<SimulationPlayback>>,
 ) {
     query.iter_mut().for_each(|(uib, mut o)| {
         o.color = match (uib, state.get()) {
-            (UiButton::Pause, SimulationState::Pause) => BLACK.into(),
-            (UiButton::Step, SimulationState::Step) => BLACK.into(),
-            (UiButton::Play, SimulationState::Run) => BLACK.into(),
+            (UiButton::Pause, SimulationPlayback::Pause) => BLACK.into(),
+            (UiButton::Step, SimulationPlayback::Step) => BLACK.into(),
+            (UiButton::Play, SimulationPlayback::Run) => BLACK.into(),
             _ => Color::NONE,
         }
     });
@@ -620,10 +653,19 @@ fn load_audio_tones(mut pitches: ResMut<Assets<Pitch>>, mut cell_assets: ResMut<
     debug_assert!(cell_assets.pitches.iter().len() == 25);
 }
 
-// TODO: Why does audio only play when running simulation?
-fn modulate_volume(mut gv: ResMut<GlobalVolume>, active: Query<Entity, With<AudioSink>>) {
-    let ratio = 1.0 / active.count() as f32;
-    gv.volume = Volume::Linear(ratio);
+fn control_volume(state: ResMut<State<AudioPlayback>>, mut sinks: Query<&mut AudioSink>) {
+    match state.get() {
+        AudioPlayback::Play => {
+            let ratio = 1.0 / sinks.count() as f32;
+            let volume = Volume::Linear(ratio);
+            sinks.iter_mut().for_each(|mut sink| {
+                sink.set_volume(volume);
+            })
+        },
+        AudioPlayback::Mute => sinks.iter_mut().for_each(|mut sink| {
+            sink.set_volume(Volume::SILENT);
+        }),
+    }
 }
 
 fn load_materials(
@@ -710,3 +752,18 @@ fn set_pan_state(
 fn is_panning(panning: Res<Panning>) -> bool {
     panning.0
 }
+
+fn toggle_state_entities<S: States + Component>(
+    mut query: Query<(&mut Visibility, &S)>,
+    state: Res<State<S>>,
+) {
+    query.iter_mut().for_each(|(mut v, s)| {
+        *v = if state.get() == s {
+            Visibility::Inherited
+        } else {
+            Visibility::Hidden
+        };
+    });
+}
+
+// TODO: Do not spawn cell when clicking UI