diff --git a/src/simulator/gui.odin b/src/simulator/gui.odin
index b433ddc..677fe42 100644
--- a/src/simulator/gui.odin
+++ b/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 {
diff --git a/src/simulator/gui_control_bar.odin b/src/simulator/gui_control_bar.odin
index b037b2c..3ab68f0 100644
--- a/src/simulator/gui_control_bar.odin
+++ b/src/simulator/gui_control_bar.odin
@@ -1,6 +1,8 @@
 package simulator
 
 import "core:log"
+
+import emu "../machine"
 import rl "vendor:raylib"
 
 gui_control_bar :: proc(rect: rl.Rectangle, sim: ^Simulator) {
@@ -15,7 +17,6 @@ gui_control_bar :: proc(rect: rl.Rectangle, sim: ^Simulator) {
 	if btn(&cursor, rect, BUTTON_HEIGHT, BUTTON_WIDTH, PADDING_X, "RUN") {
 		if sim.rom_loaded {
 			sim.paused = false
-			sim.running = true
 		} else {
 			log.info("no rom selected, can't run")
 		}
@@ -23,12 +24,26 @@ gui_control_bar :: proc(rect: rl.Rectangle, sim: ^Simulator) {
 
 	if btn(&cursor, rect, BUTTON_HEIGHT, BUTTON_WIDTH, PADDING_X, "PAUSE") {
 		sim.paused = true
-		sim.running = false
+	}
+
+	if btn(&cursor, rect, BUTTON_HEIGHT, BUTTON_WIDTH, PADDING_X, "STEP") {
+		if !sim.step do sim.step = true
 	}
 
 	if btn(&cursor, rect, BUTTON_HEIGHT, BUTTON_WIDTH, PADDING_X, "RESET") {
-
+		sim.paused = true
+		sim.disasm_count = 0
+		emu.reset_machine(sim.machine)
 	}
+
+	// @TODO: Get this working
+	slider_rect := rl.Rectangle{
+		x = rect.width - 100 - 50,
+		y = rect.y + 15,
+		width = 100,
+		height = 15
+	}
+	rl.GuiSlider(slider_rect, "Speed  ", nil, &sim.speed_value, 0, 100)
 }
 
 btn :: proc(cursor: ^f32, rect: rl.Rectangle, h, w, gap: f32, label: cstring) -> bool {
diff --git a/src/simulator/gui_file_loader.odin b/src/simulator/gui_file_loader.odin
index fc20d07..a71eb55 100644
--- a/src/simulator/gui_file_loader.odin
+++ b/src/simulator/gui_file_loader.odin
@@ -7,12 +7,6 @@ import rl "vendor:raylib"
 import emu "../machine"
 import tfd "../../external/tinyfiledialogs"
 
-Instruction :: struct {
-	address: u16,
-	raw:	 u16,
-	str:     string
-}
-
 gui_file_loader :: proc(rect: rl.Rectangle, sim: ^Simulator) {
 	rl.DrawRectangleLinesEx(rect, 1, rl.GRAY)
 
diff --git a/src/simulator/gui_status_bar.odin b/src/simulator/gui_status_bar.odin
index 14a1bf3..798ff3b 100644
--- a/src/simulator/gui_status_bar.odin
+++ b/src/simulator/gui_status_bar.odin
@@ -12,7 +12,7 @@ gui_status_bar :: proc(rect: rl.Rectangle, sim: ^Simulator) {
     cursor: f32 = rect.x + PADDING_X
     cy := rect.y + rect.height * 0.5
 
-    if sim.running && !sim.paused {
+    if !sim.paused {
         status_icon(&cursor, cy, rl.GREEN, .CIRCLE, "Running", sim.font)
     } else {
         status_icon(&cursor, cy, rl.RED, .SQUARE, "Paused", sim.font)
diff --git a/src/simulator/simulator.odin b/src/simulator/simulator.odin
index 86f6ee9..c9d7c3d 100644
--- a/src/simulator/simulator.odin
+++ b/src/simulator/simulator.odin
@@ -3,18 +3,32 @@ package simulator
 import emu "../machine"
 import rl "vendor:raylib"
 
+// CHIP-8 ROM can be at most 3584 bytes (4096 - 0x200 reserved)
+// Each instruction is 2 bytes, 3584 / 2 = 1792 instructions.
+MAX_INSTRUCTIONS :: 1792
+
+Instruction :: struct {
+	address: u16,
+	raw:	 u16,
+	str:     [32]u8
+}
+
 Simulator :: struct {
 	// Emulator
 	machine:		   ^emu.System,
 	rom_loaded:		   bool,
-	running:		   bool,
 	paused:			   bool,
+	step:			   bool,
 	cycles_per_second: int,
+	speed_value:	   f32,
 	// GUI
 	font:			   rl.Font,
 	active_tab:		   i32,
 	mem_scroll:        rl.Vector2,
-	disasm:		       []Instruction,
+	// disassembly props
+	disasm:		       [MAX_INSTRUCTIONS]Instruction,
+	disasm_follow:	   bool,
+	disasm_count:	   int,
 	disasm_scroll:     rl.Vector2,
 }
 
@@ -23,9 +37,10 @@ run_simulator :: proc(s: ^emu.System) {
 	sim := Simulator {
 		machine = s,
 		rom_loaded = false,
-		running = false,
 		paused = true,
-		cycles_per_second = 12
+		step = false,
+		cycles_per_second = 12,
+		disasm_follow = true
 	}
 
 	run_gui(&sim)