Fix keypad and drawing bugs, add drawing refresh wait

chip-8.fln

@@ -1,5 +1,4 @@
 import rl "vendor:raylib"
-import agent "vendor:agent"
 
 struct Instruction
   full: u16
@@ -10,12 +9,6 @@ struct Instruction
   nn: u8
   nnn: u16
 
-struct DrawCommand
-  x: u8
-  y: u8
-  pixels: u8
-  addr: u16
-
 struct Cpu
   pc: u16
   sp: u8
@@ -30,17 +23,22 @@ struct Machine
   delay-timer: u8
   sound-timer: u8
 
-struct State
+class State
   screen-pixels: [2048 rl/Color]
   screen-texture: rl/Texture2D
+  audio-stream: rl/AudioStream
   font: rl/Font
-  draw-commands: Vec(DrawCommand)
   page: int
+  fullscreen: bool
+  step-mode: bool
   clear-screen: bool
+  pending-key: u8?
   shift-vx-swap: bool
   jump-xnn: bool
+  skip-overflow-FX1E: bool
+  inc-index-0xFX-55-65: bool
 
-const font: [80 u8] =
+const font: [_ u8] =
   [0xF0, 0x90, 0x90, 0x90, 0xF0, ;; 0
    0x20, 0x60, 0x20, 0x20, 0x70, ;; 1
    0xF0, 0x10, 0xF0, 0x80, 0xF0, ;; 2
@@ -58,61 +56,149 @@ const font: [80 u8] =
    0xF0, 0x80, 0xF0, 0x80, 0xF0, ;; E
    0xF0, 0x80, 0xF0, 0x80, 0x80] ;; F
 
-const keypad-mapping: [16 u8] =
+const numbers: [_ [_ u8]] =
+  [[0xF0, 0x90, 0x90, 0x90, 0xF0]  ;; 0
+   [0x20, 0x60, 0x20, 0x20, 0x70]  ;; 1
+   [0xF0, 0x10, 0xF0, 0x80, 0xF0]  ;; 2
+   [0xF0, 0x10, 0xF0, 0x10, 0xF0]  ;; 3
+   [0x90, 0x90, 0xF0, 0x10, 0x10]  ;; 4
+   [0xF0, 0x80, 0xF0, 0x10, 0xF0]  ;; 5
+   [0xF0, 0x80, 0xF0, 0x90, 0xF0]  ;; 6
+   [0xF0, 0x10, 0x20, 0x40, 0x40]  ;; 7
+   [0xF0, 0x90, 0xF0, 0x90, 0xF0]  ;; 8
+   [0xF0, 0x90, 0xF0, 0x10, 0xF0]  ;; 9
+   [0xF0, 0x90, 0xF0, 0x90, 0x90]  ;; A
+   [0xE0, 0x90, 0xE0, 0x90, 0xE0]  ;; B
+   [0xF0, 0x80, 0x80, 0x80, 0xF0]  ;; C
+   [0xE0, 0x90, 0x90, 0x90, 0xE0]  ;; D
+   [0xF0, 0x80, 0xF0, 0x80, 0xF0]  ;; E
+   [0xF0, 0x80, 0xF0, 0x80, 0x80]] ;; F
+
+const keypad-mapping: [_ u8] =
   [1, 2, 3, 0xC, 4, 5, 6, 0xD, 7, 8, 9, 0xE, 0xA, 0, 0xB, 0xF]
 
-const keypad-keymap: [16 rl/Key] =
+const keypad-keymap: [_ rl/Key] =
   [:key-one, :key-two, :key-three, :key-four,
    :key-q,   :key-w,   :key-e,     :key-r,
    :key-a,   :key-s,   :key-d,     :key-f,
    :key-z,   :key-x,   :key-c,     :key-v]
 
-const hex-numbers: str = "0123456789ABCDEF"
-
-const reg-names: [16 str] = ["V0", "V1", "V2", "V3", "V4", "V5", "V6", "V7",
-                             "V8", "V9", "VA", "VB", "VC", "VD", "VE", "VF"]
-
 ;; let screen-width: int = 1300
 ;; let screen-height: int = 650
 let screen-width: int = 965
 let screen-height: int = 550
-let pixels-width: int = 64
-let pixels-height: int = 32
+let pixels-width: u8 = 64
+let pixels-height: u8 = 32
 let ips: int = 700
 let cycles: f64 = 0.0
 
-let cpu: Cpu = Cpu{}
-let machine: Machine = Machine{}
-let state: State = State{}
+once cpu: Cpu = Cpu{}
+once machine: Machine = Machine{}
+once state: State = State{}
+
+let max-samples = 512
+    max-samples-per-update = 4096
+    frequency: f64 = 440.0
+    audio-frequency: f64 = 440.0
+    sine-idx: f64 = 0.0
+    volume: f64
+    target-volume: f64
 
 fn load-rom(path: str) -> ()
   let rom = slurp(path)
-  for i, b in rom
-    machine.memory[0x200 + i] = b
+  copy(machine.memory[0x200..], rom )
 
-fn step() -> ()
-  if cpu.pc >= length(machine.memory)
+fn parse-instruction(pc: u16) -> Instruction
+  let byte1: u8 = machine.memory[pc]
+  let byte2: u8 = machine.memory[pc + 1]
+  let full = u16(byte1) << 8 | u16(byte2)
+  Instruction{.full full
+              .op (byte1 >> 4)
+              .x (byte1 & 0x0F)
+              .y (byte2 >> 4)
+              .n (byte2 & 0x0F)
+              .nn byte2
+              .nnn (full & 0x0FFF)}
+
+fn reset() -> ()
+  cpu = Cpu{}
+  machine = Machine{}
+  load-rom("./IBM Logo.ch8")
+  ;; load-rom("./vendor/chip8-test-suite/bin/1-chip8-logo.ch8")
+  ;; load-rom("./vendor/chip8-test-suite/bin/2-ibm-logo.ch8")
+  ;; load-rom("./vendor/chip8-test-suite/bin/3-corax+.ch8")
+  ;; load-rom("./vendor/chip8-test-suite/bin/4-flags.ch8")
+  ;; load-rom("./roms/Breakout [Carmelo Cortez, 1979].ch8")
+  load-rom("./roms/Brix [Andreas Gustafsson, 1990].ch8")
+  cpu.pc = 0x200
+
+fn decode-instruction(inst: Instruction) -> str
+  match inst.op
+    0x0 ->
+      match inst.nn
+        ;; TODO: Maybe this can be a draw command that clears the screen rather than special cased
+        0xE0 -> "CLS"
+        0xEE -> "RET"
+        _ -> "UNKNOWN"
+    0x1 -> format("JP 0x{:03X}", inst.nnn)
+    0x2 -> format("CALL 0x{:03X}", inst.nnn)
+    0x3 -> format("SE V{:X}, 0x{:02X}", inst.x, inst.nn)
+    0x4 -> format("SNE V{:X}, 0x{:02X}", inst.x, inst.nn)
+    0x5 -> format("SE V{:X}, V{:X}", inst.x, inst.y)
+    0x6 -> format("LD V{:X}, 0x{:02x}", inst.x, inst.nn)
+    0x7 -> format("ADD V{:X}, 0x{:02x}", inst.x, inst.nn)
+    0x8 ->
+      match inst.n
+        0x0 -> format("LD V{:X}, V{:X}", inst.x, inst.y)
+        0x1 -> format("OR V{:X}, V{:X}", inst.x, inst.y)
+        0x2 -> format("AND V{:X}, V{:X}", inst.x, inst.y)
+        0x3 -> format("XOR V{:X}, V{:X}", inst.x, inst.y)
+        0x4 -> format("ADD V{:X}, V{:X}", inst.x, inst.y)
+        0x5 -> format("SUB V{:X}, V{:X}", inst.x, inst.y)
+        0x6 -> format("SHR V{:X}, V{:X}", inst.x, inst.y)
+        0x7 -> format("SUBN V{:X}, V{:X}", inst.x, inst.y)
+        0xE -> format("SHL V{:X}, V{:X}", inst.x, inst.y)
+        _ -> "UNKNOWN"
+    0x9 -> format("SNE V{:X}, V{:X}", inst.x, inst.y)
+    0xA -> format("LD I, 0x{:03X}", inst.nnn)
+    0xB -> format("JP V0, 0x{:03X}", inst.nnn)
+    0xC -> format("RND V{:X}, 0x{:02x}", inst.x, inst.nn)
+    0xD -> format("DRW V{:X}, V{:X}, 0x{:X}", inst.x, inst.y, inst.n)
+    0xE ->
+      match inst.nn
+        0x9E -> format("SKP V{:X}", inst.x)
+        0xA1 -> format("SKNP V{:X}", inst.x)
+        _ -> "UNKNOWN"
+    0xF ->
+      match inst.nn
+        0x07 -> format("LD V{:X}, DT", inst.x)
+        0x0A -> format("LD V{:X}, K", inst.x)
+        0x15 -> format("LD DT, V{:X}", inst.x)
+        0x18 -> format("LD ST, V{:X}", inst.x)
+        0x1E -> format("ADD I, V{:X}", inst.x)
+        0x29 -> format("LD F, V{:X}", inst.x)
+        0x33 -> format("LD B, V{:X}", inst.x)
+        0x55 -> format("LD [I], V{:X}", inst.x)
+        0x65 -> format("LD V{:X}, [I]", inst.x)
+        _ -> "UNKNOWN"
+    _ -> "UNKNOWN"
+
+;; You should extract the execution from the other stuff here so you can manually
+;; run an instruction when needed, all it needs is a parsed instruction
+fn step(inst: Instruction) -> ()
+  if cpu.pc >= length(machine.memory) - 2
     cpu.pc = 0
     return
-  let byte1: u8 = machine.memory[cpu.pc]
-  let byte2: u8 = machine.memory[cpu.pc + 1]
-  let full = u16(byte1) << 8 | u16(byte2)
-  let inst = Instruction{.full full
-                         .op (byte1 >> 4)
-                         .x (byte1 & 0x0F)
-                         .y (byte2 >> 4)
-                         .n (byte2 & 0x0F)
-                         .nn byte2
-                         .nnn (full & 0x0FFF)}
+
   cpu.pc += 2
   match inst.op
     0x0 ->
       match inst.nn
         0xE0 -> state.clear-screen = true
         0xEE ->
-          cpu.pc = cpu.stack[cpu.sp]
           cpu.sp -= 1
-        _ -> println("Unrecognized 0x0 instruction")
+          cpu.pc = cpu.stack[cpu.sp]
+        _ -> print("Unrecognized 0x0 instruction")
     0x1 -> cpu.pc = inst.nnn
     0x2 -> ;; Call a subroutine
       cpu.stack[cpu.sp] = cpu.pc
@@ -122,7 +208,7 @@ fn step() -> ()
     0x4 -> if cpu.v[inst.x] != inst.nn then cpu.pc += 2
     0x5 -> if cpu.v[inst.x] == cpu.v[inst.y] then cpu.pc += 2
     0x6 -> cpu.v[inst.x] = inst.nn
-    0x7 -> cpu.v[inst.x] += inst.nn
+    0x7 -> cpu.v[inst.x] +%= inst.nn
     0x8 ->
       match inst.n
         0x0 -> cpu.v[inst.x] = cpu.v[inst.y]
@@ -134,72 +220,141 @@ fn step() -> ()
           cpu.v[inst.x] = u8(sum)
           cpu.v[0xF] = u8(sum >> 8)
         0x5 ->
-          let diff = u16(cpu.v[inst.x]) - u16(cpu.v[inst.y])
+          let diff = u16(cpu.v[inst.x]) -% u16(cpu.v[inst.y])
           cpu.v[inst.x] = u8(diff)
           cpu.v[0xF] = u8(diff >> 8 & 0x1 ^ 1)
         0x6 ->
           if state.shift-vx-swap
             cpu.v[inst.x] = cpu.v[inst.y]
           cpu.v[0xF] = cpu.v[inst.x] & 1
-          cpu.v[inst.x] = cpu.v[inst.x] >> 1
+          cpu.v[inst.x] >>= 1
         0x7 ->
-          let diff = u16(cpu.v[inst.y]) - u16(cpu.v[inst.x])
+          let diff = u16(cpu.v[inst.y]) -% u16(cpu.v[inst.x])
           cpu.v[inst.x] = u8(diff)
           cpu.v[0xF] = u8(diff >> 8 & 0x1 ^ 1)
         0xE ->
           if state.shift-vx-swap
             cpu.v[inst.x] = cpu.v[inst.y]
           cpu.v[0xF] = (cpu.v[inst.x] & 0x80) >> 7
-          cpu.v[inst.x] = cpu.v[inst.x] << 1
-        _ -> println("Unrecognized 0x8 instruction")
+          cpu.v[inst.x] <<= 1
+        _ -> print("Unrecognized 0x8 instruction")
     0x9 -> if cpu.v[inst.x] != cpu.v[inst.y] then cpu.pc += 2
     0xA -> cpu.index = inst.nnn
     0xB -> cpu.pc = inst.nnn + if state.jump-xnn then cpu.v[inst.x] else cpu.v[0]
     0xC -> cpu.v[inst.x] = u8(rand-int()) & inst.nn
-    ;; DXYN
     0xD ->
-      put(state.draw-commands, DrawCommand{.x (cpu.v[inst.x] % u8(pixels-width))
-                                           .y (cpu.v[inst.y] % u8(pixels-height))
-                                           .pixels inst.n
-                                           .addr cpu.index})
-      cpu.v[0xF] = 0
+      let x = cpu.v[inst.x] % u8(pixels-width)
+          y = cpu.v[inst.y] % u8(pixels-height)
+          collision = false
+
+      loop row in 0..inst.n
+        let byte = machine.memory[cpu.index + row]
+        let idx = i32(x) + (row + i32(y)) * i32(pixels-width)
+        loop bit in reverse(0..8)
+          if byte >> bit & 0x1 == 1 and idx < length(machine.vbuffer)
+            if machine.vbuffer[idx] then collision = true
+            machine.vbuffer[idx] = not machine.vbuffer[idx]
+          idx += 1
+
+      cpu.v[0xF] = if collision then 1 else 0
     0xE ->
-      let pressed = machine.keypad[inst.x]
-      if (inst.nn == 0x9E and pressed) or (inst.nn == 0xA1 and not pressed)
-        cpu.pc += 2
-    _ -> println("Instruction not handled: ", inst.op)
+      let pressed = machine.keypad[cpu.v[inst.x]]
+      match inst.nn
+        0x9E -> if pressed then cpu.pc += 2
+        0xA1 -> if not pressed then cpu.pc += 2
+        _ -> print("Unrecognized 0xE instruction")
+    0xF ->
+      match inst.nn
+        0x07 -> cpu.v[inst.x] = machine.delay-timer
+        0x0A -> state.pending-key = inst.x
+        0x15 -> machine.delay-timer = cpu.v[inst.x]
+        0x18 -> machine.sound-timer = cpu.v[inst.x]
+        0x1E ->
+          cpu.index += cpu.v[inst.x]
+          if not state.skip-overflow-FX1E
+            cpu.v[0xF] = u8(cpu.index >> 12)
+          cpu.index += cpu.v[inst.x]
+        0x29 -> cpu.index = cpu.v[inst.x]
+        0x33 ->
+          let vx = cpu.v[inst.x]
+          machine.memory[cpu.index + 0] = vx / 100
+          machine.memory[cpu.index + 1] = vx % 100 / 10
+          machine.memory[cpu.index + 2] = vx % 10
+        0x55 ->
+          loop i in 0..=inst.x
+            machine.memory[cpu.index + i] = cpu.v[i]
+          if state.inc-index-0xFX-55-65
+            cpu.index += inst.x
+        0x65 ->
+          loop i in 0..=inst.x
+            cpu.v[i] = machine.memory[cpu.index + i]
+          if state.inc-index-0xFX-55-65
+            cpu.index += inst.x
+        _ -> print("Unrecognized 0xF instruction")
+    _ -> print("Instruction not handled: {:X}", inst.op)
 
 fn run-update() -> ()
-  for i, key in keypad-keymap
-    machine.keypad[keypad-mapping[int(i)]] = rl/is-key-down(key)
+  loop i, key in keypad-keymap
+    machine.keypad[keypad-mapping[i]] = rl/is-key-down(key)
+    if state.pending-key as reg
+      cpu.v[reg] = u8(i)
+      state.pending-key = nil
 
   if rl/is-key-pressed(:key-minus)
     state.page = max(0, state.page - 1)
   if rl/is-key-pressed(:key-equal)
     state.page = min(5, state.page + 1)
 
-  cycles += f64(rl/get-frame-time()) * ips
+  if rl/is-key-pressed(:key-period)
+    reset()
+    return
+  if rl/is-key-pressed(:key-enter)
+    state.fullscreen = not state.fullscreen
+  if rl/is-key-pressed(:key-space)
+    state.step-mode = not state.step-mode
 
-  while cycles >= 1.0
-    step()
-    cycles -= 1.0
+  ;; Generate sound
+  if machine.sound-timer > 0
+    target-volume = 1.0
+    machine.sound-timer -= 1
+  else
+    target-volume = 0.0
 
+  if state.pending-key?
+    if machine.delay-timer > 0 then machine.delay-timer -= 1
+    return
+
+  if state.step-mode
+    if rl/is-key-pressed(:key-n) or rl/is-key-pressed-repeat(:key-n)
+      let inst = parse-instruction(cpu.pc)
+      step(inst)
+  else
+    cycles += f64(rl/get-frame-time()) * ips
+    loop cycles >= 1.0
+      let inst = parse-instruction(cpu.pc)
+      step(inst)
+      ;; Apparently on the COSMAC VIP and other devices, drawing would wait for the next scree
+      ;; refresh which ran at 60hz
+      if inst.op == 0xD
+        cycles = 0.0
+        break
+      cycles -= 1.0
+
+  fill(state.screen-pixels, rl/black)
   if state.clear-screen
     state.clear-screen = false
-    for i,pixel in machine.vbuffer
-      state.screen-pixels[i] = rl/black
   else
-    for i,pixel in machine.vbuffer
-      state.screen-pixels[i] = if pixel then rl/white else rl/black
+    loop i,pixel in machine.vbuffer
+      if pixel
+        state.screen-pixels[i] = rl/white
 
-  for i,pixel in machine.vbuffer
-    if i % 2 == 0 and i / pixels-width % 2 == 0 or i % 2 == 1 and i / pixels-width % 2 == 1
-      state.screen-pixels[i] = rl/white
+  ;; loop i,pixel in machine.vbuffer
+  ;;   if i % 2 == 0 and i / pixels-width % 2 == 0 or i % 2 == 1 and i / pixels-width % 2 == 1
+  ;;     state.screen-pixels[i] = rl/white
 
-  rl/update-texture(state.screen-texture, Ptr(const u8)(addr(state.screen-pixels)))
+  rl/update-texture(state.screen-texture, state.screen-pixels)
 
   if machine.delay-timer > 0 then machine.delay-timer -= 1
-  if machine.sound-timer > 0 then machine.sound-timer -= 1
 
 fn draw-text-normal(text: str, x: $t, y: $t, color: rl/Color) -> () where is-numeric($t)
   rl/draw-text-ex(state.font, text, rl/Vector2(f32(x), f32(y)), 21, 0.0, color)
@@ -207,58 +362,77 @@ fn draw-text-normal(text: str, x: $t, y: $t, color: rl/Color) -> () where is-num
 fn run-drawing() -> ()
   rl/clear-background(rl/black)
 
-  draw-text-normal("Keypad", 10, 200, rl/white)
-  let key-size = 25
-  for i, key in keypad-keymap
-    let x = 10 + (key-size * (i % 4))
-        y = 230 + (key-size * (i / 4))
-        color = if machine.keypad[keypad-mapping[i]] then rl/green else rl/white
-    rl/draw-rectangle-lines(x, y, key-size, key-size, color)
-    ;; TODO: Maybe we don't need hex-numbers anymore?
-    draw-text-normal(hex-numbers[i..i + 1], x + 4, y + 4, color)
-
-  draw-text-normal("Actual", 150, 200, rl/white)
-  for i,key in machine.keypad
-    let x = 150 + (key-size * (i % 4))
-        y = 230 + (key-size * (i / 4))
-        color = if machine.keypad[i] then rl/green else rl/white
-    rl/draw-rectangle-lines(x, y, key-size, key-size, color)
-    draw-text-normal("0123456789ABCDEF"[i..i + 1], x + 4, y + 4, color)
-
-  ;; Registers
-  let reg-x = 290
-  for i in 0..16
-    ;; draw-text-normal(str(i64->bytes(i64(cpu.v[i]))), 520, 60 + 26 * i, rl/white)
-    let reg-val = tformat("V{:X}=0x{:02X}", i, cpu.v[i])
-    draw-text-normal(reg-val, reg-x, 200 + 21 * i, rl/white)
-
-  let scale: f32 = 5.5
+  ;; Texture
+  let scale: f32 = if state.fullscreen then 14 else 5
       src = rl/Rectangle(0, 0, f32(pixels-width), f32(pixels-height))
       dst = rl/Rectangle(10, 10, f32(pixels-width) * scale, f32(pixels-height) * scale)
   rl/draw-texture-pro(state.screen-texture, src, dst, rl/Vector2(0.0, 0.0), 0.0, rl/white)
   rl/draw-rectangle-lines(i32(dst.x), i32(dst.y), i32(dst.width), i32(dst.height), rl/white)
 
-  for i in 0..16
+  if state.fullscreen
+    return
+
+  draw-text-normal("Keypad", 10, 200, rl/white)
+  let key-size = 25
+  loop i, key in keypad-keymap
+    let x = 10 + (key-size * (i % 4))
+        y = 230 + (key-size * (i / 4))
+        color = if machine.keypad[keypad-mapping[i]] then rl/green else rl/white
+    rl/draw-rectangle-lines(x, y, key-size, key-size, color)
+    draw-text-normal(format("{:X}", i), x + 4, y + 4, color)
+
+  ;; draw-text-normal("Actual", 150, 200, rl/white)
+  ;; loop i,key in machine.keypad
+  ;;   let x = 150 + (key-size * (i % 4))
+  ;;       y = 230 + (key-size * (i / 4))
+  ;;       color = if machine.keypad[i] then rl/green else rl/white
+  ;;   rl/draw-rectangle-lines(x, y, key-size, key-size, color)
+  ;;   draw-text-normal("0123456789ABCDEF"[i..i + 1], x + 4, y + 4, color)
+
+  ;; Instructions
+  draw-text-normal("Instructions", 125, 200, rl/white)
+  rl/draw-rectangle-lines(125, 230, 150, 100, rl/white)
+  rl/draw-rectangle(128, 258, 140, 20, rl/darkgreen)
+  loop i in 0..4
+    if cpu.pc <= 0 and i == 0
+      continue
+
+    let inst = parse-instruction(cpu.pc + u8(i) * 2 - 2)
+        text = decode-instruction(inst)
+    if text != "UNKNOWN"
+      draw-text-normal(text, 130, 235 + i * 23, rl/white)
+
+  ;; Registers
+  let reg-x = 290
+  loop i in 0..16
+    ;; draw-text-normal(str(i64->bytes(i64(cpu.v[i]))), 520, 60 + 26 * i, rl/white)
+    let reg-val = format("V{:X}=0x{:02X}", i, cpu.v[i])
+    draw-text-normal(reg-val, reg-x, 200 + 21 * i, rl/white)
+
+  ;; Stack
+  loop i in 0..16
     let row = i % 8
         col = i / 8
         x = 10
         y = 20 * row
-        w = 80
+        w = 70
         h = 20
         start-y = 360
-        idx-txt = tformat(" {:X}|", i)
+        idx-txt = format("{:X}|", i)
     rl/draw-rectangle-lines(x + col * w, start-y + y, w, h, rl/white)
-    draw-text-normal(idx-txt, x + col * w, start-y + y, rl/white)
+    draw-text-normal(idx-txt, x + 4 + col * w, start-y + y, rl/white)
     if i < cpu.sp
-      let addr-txt = tformat("0x{:02X}", cpu.stack[i])
-      draw-text-normal(addr-txt, x + 33 + col * w, start-y + y, rl/white)
+      let addr-txt = format("0x{:02X}", cpu.stack[i])
+      draw-text-normal(addr-txt, x + 24 + col * w, start-y + y, rl/white)
 
-  let x = 195
-  draw-text-normal(tformat(" i=0x{:02X}", cpu.index), x, 360, rl/white)
-  draw-text-normal(tformat("pc=0x{:02X}", cpu.sp), x, 380, rl/white)
-  draw-text-normal(tformat("dt=0x{:02}", machine.delay-timer), x, 400, rl/white)
-  draw-text-normal(tformat("st=0x{:02}", machine.sound-timer), x, 420, rl/white)
+  ;; Additional data
+  let x = 185
+  draw-text-normal(format(" i=0x{:02X}", cpu.index), x, 360, rl/white)
+  draw-text-normal(format("pc=0x{:02X}", cpu.pc), x, 380, rl/white)
+  draw-text-normal(format("dt={}", machine.delay-timer), x, 400, rl/white)
+  draw-text-normal(format("st={}", machine.sound-timer), x, 420, rl/white)
 
+  ;; Hex dump
   let hex-rows = 32
       hex-cols = 24
       padding = 4
@@ -270,29 +444,39 @@ fn run-drawing() -> ()
       grid-h = hex-rows * cell-h + padding * 2
       slots-per-page = hex-rows * hex-cols
 
-  for i in 0..4096 / slots-per-page + 1
+  loop i in 0..4096 / slots-per-page + 1
     let color = if state.page == i then rl/green else rl/white
         tab-w = 80
         start-num = i * slots-per-page
         end-num = min(4096, (i + 1) * slots-per-page)
-        tab-name = tformat("{:03X}-{:03X}", start-num, end-num - 1)
+        tab-name = format("{:03X}-{:03X}", start-num, end-num - 1)
     rl/draw-rectangle(grid-x - 1 + i * tab-w + (i * 2), grid-y - 20, tab-w, 20, color)
     draw-text-normal(tab-name, grid-x + 1 + i * tab-w + (i * 2), grid-y - 20, rl/black)
 
   rl/draw-rectangle-lines(grid-x, grid-y, grid-w, grid-h, rl/white)
-  for r in 0..hex-rows
-    for c in 0..hex-cols
+  loop r in 0..hex-rows
+    loop c in 0..hex-cols
       let idx = c + r * hex-cols + hex-cols * hex-rows * state.page
       if idx < length(machine.memory)
-        let reg-val = tformat("{:02X}", machine.memory[idx])
-        let x-padding = if c % 2 == 0 then 2 else -2
-        draw-text-normal(reg-val, grid-x + x-padding + c * cell-w, grid-y + padding + r * cell-h, rl/white)
+        let reg-val = format("{:02X}", machine.memory[idx])
+            x-padding = if c % 2 == 0 then 2 else -2
+            x = grid-x + x-padding + c * cell-w
+            y = grid-y + padding + r * cell-h
+        if idx == cpu.pc
+          rl/draw-rectangle(x, y + 2, 38, 15, rl/darkgreen)
+        if idx == cpu.index
+          rl/draw-rectangle(x, y + 2, 19, 15, rl/red)
+        draw-text-normal(reg-val, x, y, rl/white)
 
-cpu.stack[0] = 0xAA
-cpu.stack[1] = 0xAB
-cpu.stack[2] = 0xAC
-cpu.stack[3] = 0xAD
-cpu.sp = 15
+fn audio-callback-fn(buffer: Ptr(u8), frames: u32) -> ()
+  audio-frequency = frequency + (audio-frequency - frequency) * 0.95
+  let incr = audio-frequency / 44100.0
+      d = slice-from(Ptr(i16)(buffer), i32(frames))
+  loop i in 0..frames
+    volume += (target-volume - volume) * 0.002
+    d[i] = i16(32000.0 * volume * sin(2 * pi * sine-idx))
+    sine-idx += incr
+    if sine-idx > 1.0 then sine-idx -= 1.0
 
 fn main() -> i32
   rl/set-trace-log-level(:log-warning)
@@ -300,18 +484,27 @@ fn main() -> i32
   defer rl/close-window()
   rl/set-target-fps(60)
 
+  rl/init-audio-device()
+  defer rl/close-audio-device()
+  rl/set-audio-stream-buffer-size-default(max-samples-per-update)
+  ;; Init raw audio stream (sample rate: 44100, sample size: 16bit-short, channels: 1-mono)
+  state.audio-stream = rl/load-audio-stream(44100, 16, 1)
+  defer rl/unload-audio-stream(state.audio-stream)
+  rl/set-audio-stream-callback(state.audio-stream, audio-callback-fn)
+  rl/play-audio-stream(state.audio-stream)
+
   let font = rl/load-font-ex("JetBrainsMono-Regular.otf", 21, [])
   defer rl/unload-font(state.font)
   state.font = font
-  state.page = 2
   cpu.pc = 0x200
+  state.step-mode = true
   let img = rl/gen-image-color(pixels-width, pixels-height, rl/black)
   state.screen-texture = rl/load-texture-from-image(img)
   defer rl/unload-texture(state.screen-texture)
   rl/unload-image(img)
   rl/set-texture-filter(state.screen-texture, :filter-point)
 
-  until rl/window-should-close()
+  loop not rl/window-should-close()
     restart-case
       agent/poll()
       run-update()
@@ -323,8 +516,16 @@ fn main() -> i32
   0
 
 comment:
-  load-rom("./IBM Logo.ch8")
-  u8(state.memory[0x200])
-  state.memory[0x200..0x220]
-  ; (at (.memory state) (.. 0x200 0x220))
-  u16(state.memory[state.pc]) << 8 | u16(state.memory[state.pc + 1])
+  reset()
+  loop i,pixel in machine.vbuffer
+    if pixel
+      print("Row:", i / pixels-width, "Col:", i % pixels-width)
+  state.step-mode = false
+  state.step-mode = true
+  machine.sound-timer = 120
+  cpu.stack[0] = 0xAA
+  cpu.stack[1] = 0xAB
+  cpu.stack[2] = 0xAC
+  cpu.stack[3] = 0xAD
+  cpu.sp = 15
+  machine.vbuffer[8 + 12 * pixels-width + 1] = false