# Disassembly Project Index — /home/tmerritt/Projects/disassembly/

This document provides a consolidated overview of all NES disassembly projects in this directory. Each project has its own folder containing a `copilot/` subdirectory with the full source, build tooling, and an individual `OVERVIEW.md` (at the project folder root) with a detailed power-on execution flow analysis.

---

## Project Inventory

| # | Project | Region/Version | PRG Size | CHR Size | Mirroring | Build Status | Vectors (NMI / RESET / IRQ) |
|---|---------|----------------|----------|----------|-----------|--------------|------------------------------|
| 1 | Balloon Fight (JU) | Japan | 16 KB | 8 KB | Horizontal | BYTE-IDENTICAL (Pass complete) | $C094 / $C000 / $C0F7 |
| 2 | Baseball (UE) | USA/Europe | 16 KB | 8 KB | Horizontal | BYTE-IDENTICAL (Pass complete) | $C046 / $C40B / $C43E |
| 3 | Bomberman (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $C01A / $C000 / $FFF9 |
| 4 | Burger Time (U) | USA | 16 KB | 8 KB | Horizontal | BYTE-IDENTICAL (Pass complete) | $FF7F / $FD24 / $FD24 |
| 5 | Clu Clu Land (JU) | Japan | 16 KB | 8 KB | Horizontal | BYTE-IDENTICAL (Pass complete) | $C1F1 / $C196 / $C196 |
| 6 | Defender 2 (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $CAA1 / $C983 / $CA9E |
| 7 | Excitebike (JU) | Japan | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $C23B / $C184 / $FFF0 |
| 8 | Tennis (JU) | Japan | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $C07D / $C000 / $C000 |
| 9 | Pac-Man (USA) (Namco) | — | 16 KB | 8 KB | Horizontal | BYTE-IDENTICAL (Pass complete) | $C10E / $C033 / $C17E |
| 10 | Donkey Kong 3 (JUE) | Japan / USA / Europe | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $C08D / $C000 / $C000 |
| 11 | Donkey Kong Jr. (JU) | Japan | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $C6E6 / $C66E / $FFF0 |
| 12 | CIRCUS | — | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $C05A / $C000 / $4CB7 |
| 13 | Wild Gunman (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass Pass 1 redone) | $C086 / $C000 / $C000 |
| 14 | Joypad Test Cartridge (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass 3 complete) | $CCF7 / $C000 / $C000 |
| 15 | NES PowerPad Test Card (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $E06E / $E000 / $E000 |
| 16 | MUSCLE (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass complete) | $86CB / $8000 / $8764 |
| 17 | Lunar Pool (U) | USA | 16 KB | 8 KB | Vertical | BYTE-IDENTICAL (Pass 2 complete, Pass 3 tables named) | $FF65 / $E80C / $FF64 |
| 18 | `Donkey Kong (JU)` | Japan | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 2 complete, 76.3% code)** | $C85F / $C79E / $FFF0 |
| 19 | `Donkey Kong Jr. Math (U)` | USA | 16 KB | 8 KB | Vertical | **PRG-IDENTICAL (Pass 2 complete, 81.9% code)** | $C4A9 / $C41E / $FFF0 |
| 20 | `Duck Hunt (JUE)` | Japan / USA / Europe | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 2 complete, 37.5% code)** | $C086 / $C000 / $C000 |
| 21 | `Golf (JU)` | Japan | 16 KB | 8 KB | Vertical | PRG-IDENTICAL (Pass 1+ substantial) | $C0A6 / $C000 / $C0C4 |
| 22 | `Hogan's Alley (JU)` | Japan | 16 KB | 8 KB | Vertical | **PRG-IDENTICAL (Pass 1 complete, 41.8% code, needs CDL reclass)** | $C088 / $C000 / $C000 |
| 23 | `Ice Climber (JE)` | — | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 2 complete, 74.7% code)** | $C076 / $C014 / $FFF0 |
| 24 | `Ice Climber (U)` | USA | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 2 complete, 74.7% code)** | $C076 / $C014 / $FFF0 |
| 25 | `Lode Runner (U)` | USA | 16 KB | 8 KB | Vertical | **PRG-IDENTICAL (Pass 1 complete, 52.6% code)** | $C02C / $C000 / $FFF9 |
| 26 | `Mario Bros (JU)` | Japan | 16 KB | 8 KB | Vertical | PRG-IDENTICAL (Pass 1 complete, Pass 2 substantial) | $C07D / $C000 / $C000 |
| 27 | `Millipede (U)` | USA | 16 KB | 8 KB | Vertical | **PRG-IDENTICAL (Pass 1 complete, 74.6% code)** | $C7F1 / $C735 / $FFF0 |
| 28 | `Pac-Man (Tengen) (U)` | USA | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 1 complete, 19.5% code)** | $C0FA / $C033 / $C16A |
| 29 | `Pac-Man (U)` | USA | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 1 complete, 19.6% code)** | $C0FA / $FF00 / $C16A |
| 30 | `Pinball (JU)` | Japan | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 2 complete, 59.5% code)** | $C1ED / $C000 / $C1ED |
| 31 | `Popeye (JU) (PRG 0)` | — | 16 KB | 8 KB | Vertical | **PRG-IDENTICAL (Pass 1 complete, 72.3% code)** | $C701 / $C649 / $FFF0 |
| 32 | `Popeye (JU) (PRG 1)` | — | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 1 complete, 72.3% code)** | $C701 / $C649 / $FFF0 |
| 33 | `Pyramid (U)` | USA | 16 KB | 8 KB | Vertical | PRG-IDENTICAL (Pass 1 done) | $D72E / $FF00 / $FF00 |
| 34 | `Raid on Bungeling Bay (U)` | USA | 16 KB | 8 KB | Vertical | **PRG-IDENTICAL (Pass 1 complete, 64.6% code)** | $C04C / $C000 / $C2C0 |
| 35 | `Raid on Bungeling Bay (U) [a2]` | — | 16 KB | 8 KB | Horizontal | **PRG-IDENTICAL (Pass 1 complete, 64.3% code)** | $C04C / $C000 / $C2C0 |
| 36 | Urban Champion (JU) | Japan | 16 KB | 8 KB | Vertical | **BYTE-IDENTICAL (Pass 3 complete, 33.9% code)** | $CA91 / $CA00 / $CA00 |

All 36 are mapper 0 / 16 KB PRG / 8 KB CHR, battery-backed, no trainer.

Rows 1-17 are **BYTE-IDENTICAL**: `make` compares the whole reconstructed ROM
against `copilot/rom.nes`. Rows 18-36 are **PRG-IDENTICAL**: their Makefiles
compare only `reconstructed_prg.bin` against `prg.bin`, so header and CHR are
not yet proven to rebuild. Treat those as unverified outside the PRG.

**How to read this table.** The vectors are the three little-endian words at the **end of the
16 KB PRG** (`$FFFA-$FFFF` in the `$C000` mirror) — *not* fields in the iNES header, whose bytes
0-9 carry only sizes, mirroring and mapper. Regenerate the whole column with:

```bash
python3 - <<'EOF'
import os
for p in sorted(d for d in os.listdir('.') if os.path.isdir(os.path.join(d, 'copilot'))):
    rom = open(f"{p}/copilot/rom.nes", 'rb').read()
    prg = rom[16:16 + rom[4]*16384]; vo = len(prg) - 6
    v = [prg[vo+i] | (prg[vo+i+1] << 8) for i in (0, 2, 4)]
    print(f"{p:30s} {'Vertical' if rom[6] & 1 else 'Horizontal':10s} "
          + " / ".join("$%04X" % x for x in v))
EOF
```

Five rows were wrong before this pass, all from copy-paste duplication of a neighbouring row's
vectors, and are corrected above:

| Project | Was | Actually |
|---------|-----|----------|
| Burger Time (U) | `$C046 / $C40B / $C43E` (Baseball's) | `$FF7F / $FD24 / $FD24` |
| Clu Clu Land (JU) | `$C1F1 / $C000 / $FFF9` | `$C1F1 / $C196 / $C196` |
| Excitebike (JU) | `$C1F1 / $FD24 / $FD24` | `$C23B / $C184 / $FFF0` |
| Pac-Man (USA) (Namco) | `$C10E / $C000 / $C17E` | `$C10E / $C033 / $C17E` |
| Donkey Kong 3 (JUE) | `$C07D / $C000 / $C000` | `$C08D / $C000 / $C000` |

Donkey Kong Jr.'s mirroring was also wrong (Horizontal, actually Vertical). Odd vector *targets*
are not mistakes: Burger Time's `$FF7F` NMI and CIRCUS's `$4CB7` IRQ point into unused/data space,
which is common in this set — see "Notes" under Per-Project Details.

Region/Version comes from the folder-name suffix (JU/U/UE/JUE); these mapper-0 headers do not
encode region, so CIRCUS — whose folder carries no suffix — is left as `—` rather than guessed.

---

## Per-Project Details

### 1. Balloon Fight (JU)
- **Folder:** `Balloon Fight (JU)/`
- **ROM:** `balloon.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (8,538 lines)
- **Linker:** PRG at $C000, 16 KB; single segment
- **Vectors:** NMI → $C094 (`NmiHandler`), RESET → $C000 (`Reset`), IRQ → $C0F7 (`IrqHandler`, self-loop)
- **Key subsystems:** NMI-driven frame loop with PPU command buffer, round spawner ($C790), bonus objects ($CB74), carrier/rescue sequence ($C6F9), particle system ($CDAA), sound driver ($FFF7 banked)
- **Build fix:** None needed; byte-identical out of the box. **Pass 1 verified complete 2026-10-16** — 5,303 instructions / 11,260 code bytes (68.7%), which is *more* than the complete-opcode static tracer finds (5,277 / 11,202); the 166 tracer-only bytes are genuine data (command scripts at $D437/$D45A, the $C3B5 pointer table, the arithmetic table at $FBCA), not missed code. The last two `.incbin` spans were converted to explicit classified bytes (`TrailingFillBeforeApuTables` at $F4C5, `SoundEngineTailBytes` at $F5FC), so no ROM byte is hidden
- **Details:** `Balloon Fight (JU)/OVERVIEW.md`

### 2. Baseball (UE)
- **Folder:** `Baseball (UE)/`
- **ROM:** `baseball.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (21,624 lines — largest source)
- **Linker:** PRG at $C000, 16 KB; single segment
- **Vectors:** NMI → $C046 (`NMI`), RESET → $C40B (`Reset`), IRQ → $C43E (`IRQ`, `rti`)
- **Key subsystems:** Queued event system ($EB66–$EB9C) as the main frame driver, round/state machine ($C5FE), batting/pitching ($C6044–$C6414), object sorting ($C339), sound driver ($F9D0–$FE2x)
- **Build fix:** None needed; byte-identical out of the box
- **Details:** `Baseball (UE)/OVERVIEW.md`

### 3. Bomberman (U)
- **Folder:** `Bomberman (U)/`
- **ROM:** `bomberman.nes` (24,592 bytes)
- **Source:** `copilot/main.s` (8,070 lines)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (16 KB), CHR at $0000 (8 KB)
- **Vectors:** NMI → $C01A (`NmiHandler`), RESET → $C000 (`Reset`), IRQ → $FFF9 (`IrqHandler`, `rti`)
- **Key subsystems:** NMI-driven PPU command queue and VRAM transfers, main loop at $C368 with state dispatch table ($C75D), bomb/object object slots (80 slots at $03E6), sound driver ($E642–$FE2x) with dispatch table ($E6AD)
- **Build fix:** One-byte mismatch at CPU $E70C (`dec $E4` vs `dec $54`) — resolved by adding `RandomStateAlt = $E4` to `locals.inc` alongside `RandomState0 = $54` (zero-page reuse); also renamed `ControllerState` → `ControllerState1`, `Main_HandleControl_C368` → `MainGameLoop`, `Gameplay_HandleControl_C79D` → `GameplayUpdate`, `Sound_HandleControl_E65F` → `SoundUpdate`
- **Details:** `Bomberman (U)/OVERVIEW.md`

### 4. Burger Time (U)
- **Folder:** `Burger Time (U)/`
- **ROM:** `Burger Time (U) [!].nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (9,323 lines), `copilot/header.s`, `copilot/chr.s`
- **Linker:** HEADER, PRG at $C000 (0x3FFA), VECTORS at $FFFA, CHR
- **Vectors:** NMI → $FF7F (points *into* the vector page itself — not a real handler; NMI is effectively unused), RESET → $FD24 (`ResetHandler`, `sei` prologue), IRQ → $FD24 (reuses Reset)
- **Key subsystems:** Event-driven main loop via `CommonEngineExit` ($EB6A) and queued events ($EB9D), title screen / round state machine ($C5FE), object arrays ($03E6 state, $0436/$0486 position), audio engine ($F9D0–$FE2x) with music sequencer ($FD34)
- **Build fix:** None needed; byte-identical. Requires symlink `burger_time.nes → "../Burger Time (U) [!].nes"` due to spaces in ROM filename
- **Details:** `Burger Time (U)/OVERVIEW.md`

### 5. Clu Clu Land (JU)
- **Folder:** `Clu Clu Land (JU)/`
- **ROM:** `rom.nes` (24,592 bytes)
- **Source:** `copilot/main.s` (9,150 lines)
- **Linker:** PRG at $C000, 16 KB; single segment (no separate HEADER/CHR segments in cfg, but CHR data is embedded inline at end of prg.s)
- **Vectors:** NMI → $C1F1 (`NMIHandler`), RESET → $C196 (`ResetEntry`, shared with the IRQ handler), IRQ → $C196 (`IrqHandler`, reuses Reset)
- **Key subsystems:** State-machine main loop via dispatch table at $C000–$C00D, NMI-driven PPU command queue + VRAM transfers, object pools ($03E6 state, $0436/$0486 position), sound driver ($E642–$F7C0) with dispatch table ($E6AD)
- **Build fix:** One `bpl` branch to undefined label at CPU $FAB4 — replaced with `bne *-$1B` to produce original `d0 e3` bytes (disassembler mislabeled `bne` as `bpl`)
- **Details:** `Clu Clu Land (JU)/OVERVIEW.md`

### 6. Defender 2 (U)
- **Folder:** `Defender 2 (U)/`
- **ROM:** `Defender 2 (U).nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (11,905 lines)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (0x3FFA), VECTORS at $FFFA, CHR at $0000
- **Vectors:** NMI → $CAA1 (`NmiHandler`), RESET → $C983 (`ResetHandler`), IRQ → $CA9E (`IrqHandler`, reuses Reset)
- **Key subsystems:** Event-driven main loop (`UpdateSideScrollingGameplay_CA6A` at $CA6A) waiting on NMI flag, side-scrolling gameplay ($C073–$C324 family), PPU streaming ($F20B–$F7C0), audio engine ($E642–$F7C0) with dispatch table ($E6AD)
- **Build fix:** Same `bpl` → `bne *-$1B` fix at CPU $E811 as Clu Clu Land (disassembler mislabeled `bne` as `bpl`)
- **Details:** `Defender 2 (U)/OVERVIEW.md`

### 7. Excitebike (JU)
- **Folder:** `Excitebike (JU)/`
- **ROM:** `rom.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (14,111 lines)
- **Linker:** PRG at $C000, 16 KB; single segment
- **Vectors:** NMI → $C23B (`NMI`), RESET → $C184 (`Reset`), IRQ → $FFF0 (points into audio data region — likely placeholder/unused)
- **Key subsystems:** NMI-driven state machine with dispatch table at $C000–$C00D (14 states), title/menu system ($C346–$C454), gameplay update chain ($C99A), race update ($C8D6), audio engine ($F8DE) with 4 channels + SFX, serial I/O over controller port $4016
- **Build fix:** Same `bpl` → `bne *-$1B` fix at CPU $FAB4 (same pattern as Clu Clu Land/Defender 2)
- **Details:** `Excitebike (JU)/OVERVIEW.md`

### 8. Tennis (JU)
- **Folder:** `Tennis (JU)/`
- **ROM:** `Tennis (JU).nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (9,268 lines)
- **Linker:** PRG at $C000, 16 KB; single segment
- **Vectors:** NMI → $C07D (`NmiHandler`), RESET → $C000 (`Reset`), IRQ → $C000 (`Reset` reused)
- **Key subsystems:** NMI-synchronized main loop (`MainLoop` at $C04F), game state machine via `MainStateHandlerTable` ($C101, 12 states), game mode state machine via `GameModeStateTable` ($CAD7, 8 states), object/sprite system with fixed-point physics, audio engine ($F8DE) with serial I/O over controller port
- **Build fix:** None needed; byte-identical out of the box
- **Details:** `Tennis (JU)/OVERVIEW.md`

### 9. Pac-Man (USA) (Namco)
- **Folder:** `Pac-Man (USA) (Namco)/`
- **ROM:** `rom.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (9,268 lines)
- **Linker:** PRG at $C000, 16 KB; single segment
- **Vectors:** NMI → $C10E (`NmiHandler`), RESET → $C033 (`Reset`; `locals.inc` defines `ResetOffset = $C033`), IRQ → $C17E (`IrqHandler`)
- **Key subsystems:** NMI-synchronized main loop (`MainLoop` at $C04F), game state machine via `MainStateHandlerTable` ($C101, 12 states), game mode state machine via `GameModeStateTable` ($CAD7, 8 states), object/sprite system with fixed-point physics, audio engine ($F8DE) with serial I/O over controller port
- **Build fix:** None needed; byte-identical out of the box
- **Details:** `Pac-Man (USA) (Namco)/OVERVIEW.md`

### 10. Donkey Kong 3 (JUE)
- **Folder:** `Donkey Kong 3 (JUE)/`
- **ROM:** `Donkey Kong 3 (JUE).nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (9,952 lines)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (16 KB), CHR at $0000 (8 KB)
- **Vectors:** NMI → $C08D (`NmiHandler`; the `prg.s` header block records it as "Pass 2 control-flow entry at CPU $C08D"), RESET → $C000 (`Reset`), IRQ → $C000 (`Reset` reused)
- **Key subsystems:** Main loop with object/game state management at $C02E–$C18D, object movement and geometry calculations ($C28E–$C683), audio engine ($F8DE+) with sound channels ($F0–$FF), PPU command buffer streaming ($C3F4+)
- **Build fix:** Build split `main.s` into `header.s`, `prg.s`, `chr.s`; added `RandomStateAlt = $E4` for `dec $E4` at CPU $E71B (zero-page reuse with `RandomState0 = $54`). **2026-10-16 — one-byte branch-target bug fixed:** the project was recorded as BYTE-IDENTICAL but had never built byte-identical. The `bne` at CPU $C14C (PRG $014C) was annotated `D0 12` (target $C160) but assembled as `D0 0D`, because it was labelled `StoreSelectedPlayerAndScreenFlags` ($C15B) instead of the routine actually at $C160. Retargeted to `ClearAudioSetGameMode` — which is also the semantically correct target for a "mode != $01" test. `cmp` now passes.
- **Details:** `Donkey Kong 3 (JUE)/copilot/OVERVIEW.md`

### 11. Donkey Kong Jr. (JU)
- **Folder:** `Donkey Kong Jr. (JU)/`
- **ROM:** `Donkey Kong Jr. (JU).nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (12,807 lines; 6,135 instructions, 266 routines, 68 data labels, 0 conflicts)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (16 KB), CHR at $0000 (8 KB)
- **Vectors:** NMI → $C6E6 (`NmiHandler`), RESET → $C66E (`ResetHandler`), IRQ → $FFF0 (stray byte, effectively unused)
- **Key subsystems:** Reset idles in a PRNG-advance loop — the entire frame state machine (title/attract/gameplay/sound) runs inside the NMI handler; VRAM/event queue at $0300 with dispatch table at $BFFE; 8-byte PRNG at $18–$1F; sound timers at $F1AF
- **Build fix:** None needed; byte-identical out of the box (`make` in `copilot/`). **Pass 1 verified complete 2026-10-16** — a full byte-accounting audit of `prg.s` confirms all 16,384 PRG bytes are emitted exactly once (6,199 instructions + 3,889 `.byte` + 16 `.word`), every emitted value equals the ROM byte, and there are zero audit-comment mismatches or duplicate addresses. No `.incbin` remains. A complete-opcode static tracer independently reaches 6,135 instructions / 12,358 code bytes (75.4%) — every one of which is already present in the file, and the file carries 121 further code bytes the tracer does not find (reached via the `DeferredTaskHandlerTable` dispatch at $BFFE). Pass 2/3 naming is complete; Pass 3 tables are named (`DeferredTaskHandlerTable`, `HudDigitDescriptorTable`, …)
- **Details:** `Donkey Kong Jr. (JU)/OVERVIEW.md`

### 12. CIRCUS
- **Folder:** `CIRCUS/`
- **ROM:** `rom.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (~12,755 lines)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (16 KB), CHR at $0000 (8 KB)
- **Vectors:** NMI → $C05A (`NmiHandler`), RESET → $C000 (`Reset`), IRQ → $4CB7 (outside mapped space — effectively unused)
- **Key subsystems:** NMI-driven frame state machine — main loop is a spin loop at $C057, all per-frame work runs in NMI; main state dispatcher at $C0D0 with 16-state pointer table; controller input with edge flags at $09; menu system with text table at $C763 ("CONTINUE", "STAGE", "SELECT", "PLAY"); palette/screen transfer via descriptor streams; VRAM queue processing; variant object state machine at $DC3F–$FE7B; audio engine with sequence data at $FABB–$FFFB
- **Build fix:** None needed; byte-identical out of the box (`make` in `copilot/`). Pass 1/2/3 complete — full code/data classification, semantic routine naming, and data table naming all done
- **Details:** `CIRCUS/OVERVIEW.md`

### 13. Wild Gunman (U)
- **Folder:** `Wild Gunman (U)/`
- **ROM:** `rom.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (~3,000 lines with routine headers)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (16 KB), CHR at $0000 (8 KB)
- **Vectors:** NMI → $C086 (`NmiHandler`), RESET → $C000 (`Reset`), IRQ → $C000 (reuses `Reset`)
- **Key subsystems:** NMI-driven frame loop — main loop is a spin loop waiting on NMI phase flag ($20); NMI handler does OAM DMA ($4014), PPU updates, and calls game logic subroutines ($C29F, $C233, $C3AC, $C265); main state dispatcher at $C0B3 based on `GameMode` ($30); reset copies sprite/OAM data from $C844 to $05F0; APU enabled via $4015 = $0F
- **Build fix:** None needed; byte-identical out of the box (`make` in `copilot/`). **Pass 1 redone 2026-10-16** — the original tracer followed only RESET/NMI/IRQ and jsr/jmp/branch targets and knew just the 151 documented opcodes, so it missed Wild Gunman's runtime dispatch (`Label_C341`'s `pla`-based computed goto puts the jump table inline right after each `jsr $C341`) and filed ~4.9 KB of real code as `.byte` data. Code coverage went **1,597 instr / 3,352 B (20.5%) → 3,956 instr / 8,085 B (49.3%)**. Pass 2 partial — routine headers and semantic naming for key routines (`Reset`, `NmiHandler`, `MainStateDispatch`, `MainLoopBody`, etc.); zero-page aliases in `locals.inc` (`GameMode`=$30, `NmiPhase`=$20, `NmiFlag`=$22, `Timer2F`=$2F, etc.). Pass 3 pending (no data tables named yet)
- **Details:** `Wild Gunman (U)/OVERVIEW.md`

### 14. Joypad Test Cartridge (U)
- **Folder:** `Joypad Test Cartridge (U)/`
- **ROM:** `rom.nes` (24,592 bytes)
- **Source:** `copilot/prg.s` (4,401 lines; 202 routines, all with described headers)
- **Linker:** HEADER at $0000 (16 bytes), PRG at $C000 (16 KB), CHR at $0000 (8 KB)
- **Vectors:** NMI → $CCF7 (`NmiHandler`), RESET → $C000 (`Reset`), IRQ → $C000 (reuses `Reset`)
- **Key subsystems:** NMI-driven frame loop — main loop spins waiting on NMI phase; NMI handler does OAM DMA ($4014), PPU scroll/control latch, and burst VRAM writes from table at $0302; `VramPtrWrite` ($CD3F) uses a return-address modification trick at `RetAddrUpdate` ($CDC8) for runtime-computed dispatch; `VramWrite` ($CDEE) sets PPU address and writes data to PPUDATA; reset clears RAM, initializes PPU ($2000=$10, $2001=$00), triggers OAM DMA, and enters main loop
- **Build fix:** Byte-identical out of the box, but **Pass 1 was badly truncated and has been redone**. It claimed 282 instructions / 580 bytes (3.5%); the tracer halted at `$C09E` on `DCP $3C20` (`$CF`), an undocumented opcode used as ordinary code, and filed 3,256 bytes of real code as `.byte`. Now **1,773 instructions / 3,836 bytes (23.4%)**, verified against a fresh trace. `nesdis.py --undocumented` supplies the 105 undocumented NMOS opcodes; ca65 V2.19 encodes none of them, so the 4 affected instructions are emitted as explicit `.byte` with the disassembly in the comment. Pass 2 then renamed all 202 labels (zero `Label_Cxxxx` left) and rewrote all 202 routine headersr all labels, semantic naming for key routines, zero-page aliases in `locals.inc` (`VramPtrLo`=$00, `PpuCtrlShadow`=$EF, `FrameCounterLo`=$53, etc.)
- **Details:** `Joypad Test Cartridge (U)/OVERVIEW.md`

### 16. MUSCLE (U)
- **Folder:** `MUSCLE (U)/`
- **ROM:** `M.U.S.C.L.E. (U).nes` (24,592 bytes); `copilot/rom.nes` is a relative symlink `../M.U.S.C.L.E. (U).nes`
- **Source:** `copilot/prg.s` (Pass 1/2/3 output, with 42 bytecode listings above the `.byte` data)
- **Linker:** HEADER at $0000 (16 bytes), **PRG at $8000 (16 KB)**, CHR at $0000 (8 KB) — the one ROM in the set mapped *low*
- **Vectors:** NMI → $86CB (`NmiHandler`), RESET → $8000 (`Reset`), IRQ → $8764 (a bare `RTI` that doubles as the NMI epilogue). Vectors themselves sit in the $C000 mirror at $FFFA.
- **Key subsystems:** bytecode VM — 40 opcodes at `$C8-$EF` handled through a table at `$9237`, everything else a literal operand. Gameplay dispatches through three jump tables plus two zero-page `jmp (zp)` calls a static descender cannot follow: 38-entry token-program pointer table at `$8CEF`, 40-entry opcode handler table at `$9237`, 16-entry handler table at `$9F2B`, 3-entry per-level VRAM-writer table at `$AC35`. Compressed-VRAM RLE decoder at `$AC82` with a 12-byte fill table at `$ACBD`; division by 20 restored at `$82AC`; four-channel sound engine with per-channel state in zero page `$C4-$EF`.
- **Build fix:** the skeleton's `$C000` linker assumption was wrong — RESET is `$8000`, so `linker.cfg` had to move. `copilot/Makefile` tool paths were `../../../_tools/` while in `_wip/`; promotion to top-level required `../../_tools/`. `make regen` (pass1→pass2→pass3) reproduces `prg.s` byte-for-byte.
- **Details:** `MUSCLE (U)/OVERVIEW.md`

---

## `_wip/` Projects

These 19 ROMs are listed as rows 18-36 of the Project Inventory above, so their
vectors and mirroring are in one place rather than a second table that can drift.

Each is a Pass-0 skeleton (`default_project.tar.gz`): `copilot/` holds the split
`prg.bin`/`header.bin`/`chr.bin` and a symbolic `prg.s`. **They verify at PRG
level only** — their Makefiles run `cmp reconstructed_prg.bin prg.bin`, not a
whole-ROM compare, which is why the inventory marks them `PRG-IDENTICAL` rather
than `BYTE-IDENTICAL`. Promoting one to the top level means adding a
`copilot/rom.nes` (a relative symlink survives the `git mv`), switching the
Makefile to a full-ROM compare, and moving the `../../../_tools/` paths to
`../../_tools/`. `Lunar Pool (U)` went through exactly that on 2026-10-18, and it
needed `header.s`, `chr.s` and a HEADER/PRG/CHR `linker.cfg` before `make` could
compare a whole ROM — a Pass-0 skeleton has none of the three.

`Pyramid (U)` is the only one with Pass 1 done. All 19 currently build cleanly.

Notable vector/header observations for Pass 1 work:
- **Pac-Man (U)** RESET at `$FF00` (vector-page tail), while the Tengen variant RESETs at `$C033` — different builds confirmed (PRG bytes differ).
- **Lunar Pool (U)** NMI `$FF65` / IRQ `$FF64` are adjacent in the vector page; RESET `$E80C`.
- **NES PowerPad Test Card (U)** — *at Pass 2/3*: minimal code (~7.2%), data-heavy test cartridge. RESET at $E000 (non-$C000 entry). NMI handler reads controllers via shift register, processes pad transitions, draws score/lives. See `NES PowerPad Test Card (U)/OVERVIEW.md`.
- **Lunar Pool (U)** — *Pass 2 and Pass 3 complete; promoted to the top level 2026-10-18*: RESET at `$E80C` (not `$C000`), NMI `$FF65`, IRQ `$FF64` (a bare `rti` just before the NMI handler, so IRQs are ignored). There is **no** `jmp ($7961)` RAM-pointer gate (an earlier claim): those three sites fell out of decoding two bytes into the word "player". `$CBDC`/`$CBC9` is a print-inline-string-and-return-after-it helper, so a `jsr $CBDC` is always followed by a `$81`-prefixed, `$00`-terminated string ("player", "shot", "game over", "hi`score__", "perfect_"). The split was re-derived from a Mesen CDL capture (10,028 bytes Code): now **5,300 instructions / 11,077 bytes (67.6%)**, 5,301 data bytes and the six vector bytes as `.word`. Pass 2 named all **705** labels — `Label_<addr>` is gone from the file — and Pass 3 named 33 tables plus the zero-page aliases (38 semantic, 66 neutral, ten former phantom aliases deleted). Residue, recorded rather than guessed: 73 bytes of *reachable* code are still `.byte` (`$EA9A`, `$EADC`, `$EAE5`, `$EAED`, `$EB04`, `$EB16-$EB4F` — the CDL capture never fetched them), another 75 bytes of ending-screen code sit at `$F5F9-$F643`, and ~206 bytes of unreached-but-clearly-code stubs stay data. The full 24,592-byte ROM (header + PRG + CHR) rebuilds byte-identically. See `Lunar Pool (U)/OVERVIEW.md`.
- **Ice Climber (JE) vs (U)**: byte-identical PRG *and* header — only the CHR differs (~regional title graphic).
- **Popeye (JU) PRG 0 vs PRG 1**: different PRG binaries (and mirroring); same vectors.
- **Raid on Bungeling Bay (U) vs [a2]**: `[a2]` differs in mirroring only per header, but PRGs differ — separate builds.
- **Pyramid (U)** — *already at Pass 1*: interesting unlicensed Sachen boot ($4100 mapper pokes, "AV" stack-byte check, two queued-event dispatchers). See its `OVERVIEW.md`.
- **CIRCUS** — *at Pass 2/3*: full recursive disassembly complete. NMI-driven frame state machine (main loop is a spin loop at $C057). Menu text at $C763 ("CONTINUE", "STAGE", "SELECT", "PLAY"). Object state machine at $DC3F–$FE7B. Audio sequence data at $FABB–$FFFB. See `CIRCUS/OVERVIEW.md`.
- **Joypad Test Cartridge (U)** — *Pass 3 complete*: minimal code (23.4%), data-heavy test cartridge. Data region `$CF06–$FFFF` broken into 20 named sub-blocks; VRAM command stream opcode set decoded via `RetAddrUpdate` return-address modification trick at `$CDC8`. See `Joypad Test Cartridge (U)/OVERVIEW.md`.
- **Wild Gunman (U)** — *Pass 1 redone, Pass 2 partial, Pass 3 pending*: NMI-driven frame loop. Gates its code behind runtime computed-goto tables — see the `prg.s` header block and its `OVERVIEW.md`.
- **Mario Bros (JU)** — *Pass 1 complete (72.2% code), Pass 2 substantial*: 252 subroutine entry points named (90 semantic + 165 `SubCxxxx` address-based); 667 internal `Label_Cxxxx` branch targets remain. Code is gated behind stack-based indirect dispatch at `$CD9E` and a 20-entry `JSR` thunk table at `$C5A3`. Audio routines in `$F8xx-$F9xx` clearly identifiable from APU register writes. See `_wip/Mario Bros (JU)/OVERVIEW.md`.

## Common Patterns Across All Projects

### Memory Map
Every project uses a single 16 KB PRG bank mapped at CPU **$C000–$FFFF**, with 8 KB CHR. All builds are NROM (no bank switching).

### Interrupt Structure
All projects follow the same NES interrupt pattern:
- **NMI** fires once per frame and is the real-time heartbeat — handles OAM DMA, PPU updates, controller reading, and audio.
- **RESET** performs cold-start hardware init, RAM clearing, and enters the main loop.
- **IRQ** is almost always unused (either `rti` or a self-loop).

Two exceptions worth noting from branches of this family:
- **Excitebike** uses a state-dispatch table at $C000 rather than a conventional inline main loop, and its IRQ vector points into a data region (unused).
- **Donkey Kong Jr.** is the extreme case: its reset path idles forever in a PRNG-advance loop, and the *entire* frame state machine (title, attract, gameplay, sound) executes inside the NMI handler itself. Its reset entry is also at $C66E rather than $C000.

### Build Toolchain
All projects use the same toolchain:
- **ca65** (6502 assembler)
- **ld65** (linker with `.cfg` memory map)
- All rebuilds are verified **byte-identical** to the original `prg.bin` / ROM PRG bank.

### Disassembly Style
All sources are "Pass-1" style disassemblies:
- Every instruction annotated with PRG offset, CPU address, and emitted bytes
- Inline `.byte`/`.word`/`.res` data blocks interleaved with code
- Address-based labels (`Label_Cxxxx`, `Sub_Cxxxx`, `EngineRoutine_Cxxxx`) where semantics are not yet resolved
- Zero-page symbol files (`locals.inc`) and hardware symbol files (`symbols.inc`)

---

## Navigation

Each project folder contains:
- `copilot/` — disassembly source, build config, and build artifacts
- `OVERVIEW.md` (at the project folder root) — detailed per-project power-on execution flow analysis
- `<rom>.nes` — original NES ROM image (for reference)

To rebuild any project:
```bash
cd /home/tmerritt/Projects/disassembly/<Project>/copilot
make
```

To verify byte-identity:
```bash
make verify   # (where supported by the Makefile)
```

---

## Pass 1 methodology note (2026-10-16)

The original Pass 1 disassembler had two limitations that silently understated
code coverage. Both are worth knowing before trusting a coverage percentage:

1. **Documented opcodes only.** Its table held the 151 documented 6502 opcodes.
   These ROMs also use the 54 undocumented opcodes and the 26 unofficial NOPs
   as 2/3-byte padding; a tracer that halts on them strands the real code behind.
2. **No runtime dispatch.** It followed only vectors and direct `jsr`/`jmp`/branch
   targets. Games here dispatch through computed jumps — `jmp ($0014)`, the
   `pla`-based inline-table gotos in Wild Gunman (`Label_C341`), and task tables
   like Donkey Kong Jr.'s `DeferredTaskHandlerTable` at $BFFE.

Effect measured per project (old tracer → complete-opcode dispatch-aware tracer):

| Project | Old | Complete | Action taken |
|---------|-----|----------|--------------|
| NES PowerPad Test Card (U) | 546 instr | 559 | Pass 1 already sound |
| Joypad Test Cartridge (U) | 282 instr | **1,773** | Pass 1 redone (23.4% code); Pass 2 complete; Pass 3 complete |
| Wild Gunman (U) | 1,600 instr | **4,083** | Pass 1 redone (49.3% code) |
| Balloon Fight (JU) | 5,216 instr | 5,277 | hand-done file was already better |
| Donkey Kong Jr. (JU) | 6,135 instr | 6,135 | file already complete |

**Joypad Test Cartridge (U) was the last project carrying the old, truncated
Pass 1, and has now been redone.** Its recorded "3.5% code" was really 23.4%: the
tracer stopped at `$C09E` on `DCP $3C20` (`$CF`), an undocumented opcode used as
ordinary code, and 3,256 bytes of real code were filed as `.byte` data. Redoing it
also invalidated its Pass 3, which had described `$C09E–$C173` and `$C17F–$CCF6` as
data — both are code. Pass 3 is now the outstanding work.

The fix generalises: `nesdis.py --undocumented` decodes all 105 undocumented NMOS
opcodes. It is **default off** so that projects whose `prg.s` is already
regen-stable keep reproducing byte-for-byte under `make regen`.

`_tools/verify_pass1.py` now checks all 36 projects. All are faithful; none is
truncated. Its comment-spelling report used to claim that **no project follows the
canonical `; CPU:$xxxx PRG:xxxx AA BB` audit-comment convention**. That was a bug in
the checker, not a fact about the sources: the `canonical` pattern ends with `$` but
was compiled without `re.MULTILINE`, so it could only ever match once — at end of
file — and every project fell through to whichever laxer spelling matched most
lines. Fixed. With `re.M` the true split across the 17 top-level projects is
**8 canonical** (CIRCUS, Excitebike, Joypad Test Cartridge, Lunar Pool, MUSCLE,
NES PowerPad Test Card, Pac-Man (USA) (Namco), Wild Gunman), 3 `pipe`, 2 `short`,
and one each of `rom`, `bytes`, `colon` and `slash` — so the checker sees seven
distinct spellings across the repo, six of them non-canonical, with canonical
dominant.

The old claim that "Excitebike and Pac-Man carry no byte comments at all" is stale
too. Pac-Man (USA) (Namco) is complete (4,695/4,695 instructions commented); the two
`_wip/Pac-Man` folders are 12-line `.incbin` Pass-0 skeletons with no disassembly to
comment. The one real gap is **Excitebike: 1,013 of its 5,376 instruction lines carry
no audit comment**, and that is now the whole of item 3 below.

Separately, `verify_pass1.py`'s re-trace half crashes on `MUSCLE (U)` and
`Donkey Kong Jr. (JU)` with `ValueError: invalid literal for int() with base 16:
':$0010'` (and `':$0002'`). `nesdis.trace()` parses an emitted operand with
`int(text[1:], 16)`, but the `a:` prefix that the emitter adds to ABS/ABSY/ABSX/IND
operands with a `$00` high byte makes the text `a:$0010` — so the slice starts on the
colon. Any project containing `jmp ($00xx)` / `jsr`/`jmp $00xx` hits it. Not fixed
here because `nesdis.py` feeds `make regen`, and MUSCLE's regen output must stay
byte-stable.

### TODO — audit comments for Excitebike and Pac-Man

Both are hand-written sources with semantic labels but **no byte-identity audit
trail**, so a source line cannot be mapped back to exact ROM bytes without
re-assembling. Everything else in this repo carries such a comment.

The approach that was going to be used, and the reason it was abandoned:

* Addresses come from `ca65 -l`. That part works — the listing prints the segment
  offset and the emitted bytes, and the offset indexes `prg.bin` directly.
  Byte *values* must be read from `prg.bin` rather than the listing, because
  ca65 prints `rr rr` for relocatable words.
* **The blocker: ca65's listing contains no source line numbers.** It emits
  `<offset>r <n>  <bytes>  <source text>` and nothing that ties an entry back to
  a line number, so entries cannot be keyed to source lines directly.

Remaining options, none of them free:

1. **Lockstep text alignment** — walk the listing and `prg.s` together, matching
   each listing entry's trailing source text against the next source line. Needs
   care: the listing may truncate long lines, and blank or comment-only source
   lines may not appear at all, so the two streams are not obviously 1:1.
2. **Re-derive offsets by decoding `prg.s` independently** — re-implement enough
   of ca65's layout to walk directives, macros and expression evaluation. High
   risk of disagreeing with ca65, and a disagreement would corrupt offsets
   silently while still assembling.
3. **Emit an intermediate from a known-good tracer** — regenerate both projects
   through `nesdis.py` for the comments only, then transplant the comments onto
   the hand-written source. Also needs a line-to-line correspondence.

Whichever is chosen, the check is the same and must not be skipped: after
inserting comments, `make` must still print `Byte-identical ROM verified.`, and
the comment's byte list must match `prg.bin` at the stated offset for every
line. A wrong offset that still assembles is the failure mode to watch for.

---

## Summary

The 16 numbered projects below are promoted out of `_wip/` and rebuild **byte-identical**
to their original ROMs. The 20 `_wip/` projects (rows 17-36) verify at PRG level only —
see "`_wip/` Projects" below.

| # | Project | Build Status | Pass 3 |
|---|---------|--------------|--------|
| 1 | Balloon Fight (JU) | BYTE-IDENTICAL | complete (Pass 1 verified) |
| 2 | Baseball (UE) | BYTE-IDENTICAL | complete |
| 3 | Bomberman (U) | BYTE-IDENTICAL | complete |
| 4 | Burger Time (U) | BYTE-IDENTICAL | complete |
| 5 | Clu Clu Land (JU) | BYTE-IDENTICAL | complete |
| 6 | Defender 2 (U) | BYTE-IDENTICAL | complete |
| 7 | Excitebike (JU) | BYTE-IDENTICAL | complete |
| 8 | Tennis (JU) | BYTE-IDENTICAL | complete |
| 9 | Pac-Man (USA) (Namco) | BYTE-IDENTICAL | complete |
| 10 | Donkey Kong 3 (JUE) | BYTE-IDENTICAL | complete |
| 11 | Donkey Kong Jr. (JU) | BYTE-IDENTICAL | complete (Pass 1 verified) |
| 12 | CIRCUS | BYTE-IDENTICAL | complete |
| 13 | Wild Gunman (U) | BYTE-IDENTICAL | pending (Pass 1 redone) |
| 14 | Joypad Test Cartridge (U) | BYTE-IDENTICAL | Pass 3 complete |
| 15 | NES PowerPad Test Card (U) | BYTE-IDENTICAL | complete |
| 16 | MUSCLE (U) | BYTE-IDENTICAL | complete |

Rows 17-36 (`_wip/`) all rebuild cleanly at PRG level. `Pyramid (U)` is the only
one with Pass 1 done. Pass 1 work and promotion into the numbered inventory is
future work for all of them.

Use `_tools/verify_pass1.py` to re-check any of this at any time; it rebuilds each
project and re-traces it, and reports `TRUNCATED` when a project's committed split
claims less code than the tracer can reach.