# Duck Hunt (JUE) — Pass 2 Complete

ROM: `_wip/Duck Hunt (JUE)/Duck Hunt (JUE).nes` (24,592 bytes, iNES). Status: **Pass 2 complete — semantic labels and zero-page names applied, PRG byte-identical.** `copilot/prg.s` contains a classified disassembly with 3,058 instructions (37.5% code), 48 semantic labels, and 174 zero-page semantic aliases. The build is **BYTE-IDENTICAL** at the PRG level.


## ROM Facts

| Property | Value |
|----------|-------|
| Mapper | 0 (NROM) — from the iNES header |
| PRG | 16 KB (header claims map at CPU $C000–$FFFF) |
| CHR | 8 KB |
| Mirroring | Horizontal |
| Battery-backed flag | clear |
| ROM SHA-256 | `ca0d31e6f3aa70204fa5af67803c6533851a28fa48a133e15d772d3667fa675a` |
| PRG SHA-256 | `bcdd22fbe343ebd33c7fd19309510079150d1e4dc052f65382b64d197d6ba080` |

## Interrupt Vectors (taken from PRG $3FFA–$3FFF)

| Vector | Target | Note |
|--------|--------|------|
| NMI | `$C086` | per-frame heartbeat |
| RESET | `$C000` | cold start at $C000 — the usual pattern in this repo |
| IRQ | `$C000` | redirects to RESET — unused placeholder |

## `copilot/` Contents

| File | Purpose |
|------|---------|
| `Duck Hunt (JUE).nes` | original ROM image (reference) |
| `prg.bin` / `header.bin` / `chr.bin` | split image, produced by `_tools/splitnes.py` |
| `prg.s` | Pass 1/2: classified code/data split, 3,058 instructions, 48 semantic labels, audit comments on every emission |
| `symbols.inc` | shared NES hardware constants (PPU/APU/controller, from the skeleton) |
| `locals.inc` | 174 zero-page semantic aliases (filled in by Pass 2) |
| `linker.cfg` | PRG at $C000, 16 KB, `fill = yes` |
| `Makefile` | links `reconstructed_prg.bin` and `cmp`s it against `prg.bin` |
| `reconstructed_prg.bin` | build output from the last verified build |

Header/CHR are reproduced verbatim from `header.bin`/`chr.bin` (not linked): `make` verifies **PRG bytes only** at this stage. When this project is promoted to a full disassembly, `header.s` / `chr.s` (as e.g. `Burger Time (U)`) and a full-ROM `make` target get added.

## Build

```bash
cd "_wip/Duck Hunt (JUE)/copilot"
make        # → cmp reconstructed_prg.bin prg.bin → "BYTE-IDENTICAL"
```

## Next Steps (per `PROMPTS.md`)

1. **Pass 3** — name data tables/structures; release provisional flags.
2. **Promotion** — move to a top-level `<name>/copilot/` folder, add full-ROM build (header.s + chr.s + vectors), and write the power-on flow `OVERVIEW.md` in the established style; then it joins the root index's numbered inventory.

## Pass 2 Details (2026-10-18)

- **Label renaming**: 48 of 472 labels renamed to semantic names using `pass2.py apply` with a mapping file (`duckhunt_label_map.tsv` + `locals.inc` for zero-page). Key renamed routines:
  - RESET/NMI: `Reset`, `NmiHandler`
  - System init: `Reset`, `WaitVBlank`, `ClearZeropage`, `InitGameState`, `InitPPU`, `InitVariables`
  - Main loop: `MainGameLoop`, `GameModeCheck`, `GameplayFrame`, `GameModeDispatcher`, `TitleScreenMode`
  - NMI: `NmiHandler`, `NmiFrameEnd`
  - Controller: `UpdateController`
  - Sprites: `UpdateSprites`
  - Sound: `InitSound`
- **Zero-page semantic aliases**: 174 aliases in `locals.inc` (see `locals.inc` header for full list):
  - PPU: `PPUCtrlShadow` ($08), `PPUMaskShadow` ($09)
  - Game state: `GameMode` ($24), `RoundIndex` ($26), `DispatchIndex` ($2A)
  - Player arrays: `PlayerState` ($16), `PlayerInput` ($25), `PlayerData` ($2A)
  - Pointers: `TempPtrLo` ($00), `TempPtrHi` ($01)