From b6b07c036ff5784ed4102e00096bef53ff3e17ea Mon Sep 17 00:00:00 2001
From: Butter <butterthebun@proton.me>
Date: Tue, 7 Apr 2026 10:48:11 -0400
Subject: [PATCH] added my checklist

---
 Cargo.lock |  2 +-
 Cargo.toml |  4 +--
 README.md  | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/cpu.rs |  7 ++--
 4 files changed, 106 insertions(+), 5 deletions(-)
 create mode 100644 README.md

diff --git a/Cargo.lock b/Cargo.lock
index 0989ea8..9991712 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -33,7 +33,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5d20789868f4b01b2f2caec9f5c4e0213b41e3e5702a50157d699ae31ced2fcb"
 
 [[package]]
-name = "buttery_chip8"
+name = "buttery8"
 version = "0.1.0"
 dependencies = [
  "minifb",
diff --git a/Cargo.toml b/Cargo.toml
index 74612a4..e233713 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,8 +1,8 @@
 [package]
-name = "buttery_chip8"
+name = "buttery8"
 version = "0.1.0"
 edition = "2024"
 
 [dependencies]
 minifb = "0.27"
-rand = "0.10"
\ No newline at end of file
+rand = "0.10"
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..795a432
--- /dev/null
+++ b/README.md
@@ -0,0 +1,98 @@
+# The buttery chip-8
+
+Just a personal project for me to get the hang of emulator development. 
+
+Load a .ch8 rom with `buttery8 filename.ch8`.
+
+# TODO
+ 
+## Project Setup
+- [x] Initialize Rust project
+- [x] Set up `Cargo.toml` with dependencies
+- [x] Set up window/display library (I went with [minifb](https://docs.rs/minifb/latest/minifb/))
+- [ ] Set up audio library
+- [x] CLI ROM loading via command line argument
+ 
+## CPU / Core
+- [x] Define CPU struct (registers, memory, stack, timers, PC, I)
+- [x] Load ROM into memory at 0x200
+- [x] Load fontset into memory at 0x050
+- [x] Fetch / decode / execute loop
+- [ ] Proper cycle timing
+ 
+## Opcodes
+- [x] `00E0` - CLS (clear display)
+- [x] `00EE` - RET (return from subroutine)
+- [x] `1nnn` - JP addr
+- [x] `2nnn` - CALL addr
+- [x] `3xkk` - SE Vx, byte
+- [x] `4xkk` - SNE Vx, byte
+- [x] `5xy0` - SE Vx, Vy
+- [x] `6xkk` - LD Vx, byte
+- [x] `7xkk` - ADD Vx, byte
+- [x] `8xy0` - LD Vx, Vy
+- [x] `8xy1` - OR Vx, Vy
+- [x] `8xy2` - AND Vx, Vy
+- [x] `8xy3` - XOR Vx, Vy
+- [x] `8xy4` - ADD Vx, Vy (with carry)
+- [x] `8xy5` - SUB Vx, Vy (with borrow)
+- [x] `8xy6` - SHR Vx
+- [x] `8xy7` - SUBN Vx, Vy (with borrow)
+- [x] `8xyE` - SHL Vx
+- [x] `9xy0` - SNE Vx, Vy
+- [x] `Annn` - LD I, addr
+- [x] `Bnnn` - JP V0, addr
+- [x] `Cxkk` - RND Vx, byte
+- [x] `Dxyn` - DRW Vx, Vy, nibble (draw sprite)
+- [x] `Ex9E` - SKP Vx (skip if key pressed)
+- [x] `ExA1` - SKNP Vx (skip if key not pressed)
+- [x] `Fx07` - LD Vx, DT (read delay timer)
+- [ ] `Fx0A` - LD Vx, K (wait for key press)
+- [x] `Fx15` - LD DT, Vx (set delay timer)
+- [x] `Fx18` - LD ST, Vx (set sound timer)
+- [x] `Fx1E` - ADD I, Vx
+- [x] `Fx29` - LD F, Vx (set I to font sprite)
+- [x] `Fx33` - LD B, Vx (BCD conversion)
+- [x] `Fx55` - LD [I], Vx (store registers to memory)
+- [x] `Fx65` - LD Vx, [I] (read registers from memory)
+ 
+## Display
+- [x] 64x32 pixel framebuffer
+- [x] XOR sprite drawing
+- [x] Set VF on sprite collision
+- [x] Render framebuffer to window
+- [ ] Correct draw timing / refresh rate
+ 
+## Input
+- [x] Map keyboard to CHIP-8 hex keypad (0x0-0xF)
+- [ ] Key pressed state
+- [ ] Key released state
+- [ ] Blocking wait for keypress (`Fx0A`)
+ 
+## Timers
+- [ ] Delay timer counts down at 60hz
+- [ ] Sound timer counts down at 60hz
+- [ ] Buzzer sounds while sound timer > 0
+ 
+## Audio
+- [ ] Generate beep / tone while sound timer active
+ 
+## Testing & Compatibility
+- [x] Pass `1-chip8-logo.ch8`
+- [x] Pass `2-ibm-logo.ch8`
+- [x] Pass `3-corax+.ch8`
+- [x] Pass `4-flags.ch8`
+- [ ] Pass `5-quirks.ch8`
+- [ ] Pass `6-keypad.ch8`
+- [ ] Pass `7-beep.ch8`
+- [ ] Pass `8-scrolling.ch8`
+- [ ] Test with real ROMs / games
+ 
+## Polish
+- [ ] Configurable CPU speed / cycles per frame
+- [ ] Configurable color palette
+- [ ] Window scaling / resize support
+- [ ] Pause / resume
+- [ ] Reset / reload ROM
+- [ ] SUPER-CHIP / CHIP-48 quirks mode (optional)
+- [ ] XO-CHIP support (optional)
\ No newline at end of file
diff --git a/src/cpu.rs b/src/cpu.rs
index 9a7cba3..40d0f56 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -139,7 +139,9 @@ impl Cpu {
                     self.reg[x] = result;
                     self.reg[0xF] = not_borrow;
                 }
-                0xE => {
+                0xE => {    //8xyE - SHL Vx {, Vy}
+                            //Set Vx = Vx SHL 1.
+                            //If the most-significant bit of Vx is 1, then VF is set to 1, otherwise to 0. Then Vx is multiplied by 2.
                     self.reg[x] = self.reg[y];
                     let msb = (self.reg[x] >> 7) & 1;
                     self.reg[x] <<= 1;
@@ -205,7 +207,8 @@ impl Cpu {
                 0x29 => {
                     self.index = ((self.reg[x] * 5) + 0x050) as u16;
                 }
-                0x33 => {
+                0x33 => {   // BCD conversion isn't something I've encountered before
+                            // Very interesting op
                     let vx = self.reg[x];
                     let hundreds = vx / 100;
                     let tens = (vx / 10) % 10;