Step, reset, tick_timer proc and struct cleanup.

Added a tick_timer proc so the code handles the step neatly.
Added some new struct fields to accomodate this and moved danglings
struct defs into the simulator definition.

src/simulator/gui.odin

@@ -67,23 +67,19 @@ run_gui :: proc(sim: ^Simulator) {
 		layout := calc_layout(screen_width, screen_height)
 
 		rl.BeginDrawing()
-		rl.ClearBackground(rl.BLACK)
+		rl.ClearBackground(rl.Color{0x18, 0x18, 0x18, 0xFF})
 
 		if (!sim.paused) {
 			// Cycle the machine to update memory etc
 			emu.run_machine(sim.machine, 12)
+			tick_timers(sim, beep)
+		}
 
-			// Handle delay timer
-			if sim.machine.delay_timer > 0 do sim.machine.delay_timer -= 1
-
-			// Current sound file is around 1s so stop
-			// immediately when timer is 0
-			if sim.machine.sound_timer > 0 {
-				sim.machine.sound_timer -= 1
-				if !rl.IsSoundPlaying(beep) do rl.PlaySound(beep)
-			} else {
-				rl.StopSound(beep)
-			}
+		if(sim.paused && sim.step) {
+			// Cycle the machine to update memory etc
+			emu.run_machine(sim.machine, 1)
+			tick_timers(sim, beep)
+			sim.step = false
 		}
 
 		// Top
@@ -115,9 +111,16 @@ run_gui :: proc(sim: ^Simulator) {
 	rl.UnloadSound(beep)
 	rl.CloseAudioDevice()
 	rl.CloseWindow()
+}
 
-	// Free any allocated memory for the simulator
-	delete(sim.disasm)
+tick_timers :: proc(sim: ^Simulator, beep: rl.Sound) {
+    if sim.machine.delay_timer > 0 do sim.machine.delay_timer -= 1
+    if sim.machine.sound_timer > 0 {
+        sim.machine.sound_timer -= 1
+        if !rl.IsSoundPlaying(beep) do rl.PlaySound(beep)
+    } else {
+        rl.StopSound(beep)
+    }
 }
 
 calc_layout :: proc(screen_width: f32, screen_height: f32) -> Layout {