# Ice Climber (U) — Pass 1 Disassembly

ROM: `_wip/Ice Climber (U)/Ice Climber (U).nes` (24,592 bytes, iNES). Status: **Pass 1 complete — 74.6% code; Pass 2 not started.** `copilot/prg.s` is a real disassembly, not a skeleton: 6,112 instructions (12,230 bytes as code), **973 label definitions of which only 2 carry semantic names** (`Reset`, `NmiHandler`) — the other 971 are address-based `Label_`. `locals.inc` holds **157 neutral `ZpXX` slots and no semantic zero-page aliases**. It builds **byte-identical** at the PRG level (`cmp reconstructed_prg.bin prg.bin`).

**Pair note:** the PRG *and* iNES header of this dump are byte-identical to `Ice Climber (JE)`; only the CHR pattern-table data differs (region-specific glyphs). The two `prg.s` files are *not* identical — `(JE)` has had a partial Pass 2 (76 names) applied, this variant has not.

The 2026-10-19 doc-drift sweep retitled this file from "Skeleton Project" to "Pass 2 complete" while correctly noting the 971 `Label_` definitions in the same paragraph. That was a copy-paste error from `Ice Climber (JE)`; the sweep's own text contradicted itself, and no Pass 2 map file exists for `(U)` (unlike `(JE)`). Corrected here.


## 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 | `de0ff27935752e0b5a7840d1f4ae9fe04f89236be0af79f5554fbf4f1f17d427` |
| PRG SHA-256 | `6913935b8d55ade070555416d330472839f4cefbf865c15c8248796d2bc5cf29` |

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

| Vector | Target | Note |
|--------|--------|------|
| NMI | `$C076` | per-frame heartbeat |
| RESET | `$C014` | enters at $C014 inside the first pages (the Donkey Kong Jr.-style non-$C000 entry) |
| IRQ | `$FFF0` | lands in the vector-page padding — unused placeholder |

## `copilot/` Contents

| File | Purpose |
|------|---------|
| `Ice Climber (U).nes` | original ROM image (reference) |
| `prg.bin` / `header.bin` / `chr.bin` | split image, produced by `_tools/splitnes.py` |
| `prg.s` | Pass-1 disassembly: 6,112 instructions, 971 address-based `Label_` labels + `Reset`/`NmiHandler`, canonical audit comments |
| `symbols.inc` | shared NES hardware constants (PPU/APU/controller) |
| `locals.inc` | 157 neutral `ZpXX` zero-page slots (Pass 2 naming outstanding) |
| `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 not linked: `copilot/` keeps the raw `header.bin`/`chr.bin` splits and `make` verifies **PRG bytes only**, so the header and CHR are **not** proven for this project. Promotion to the top level adds `header.s` / `chr.s` (as e.g. `Burger Time (U)`), a HEADER/PRG/CHR `linker.cfg`, and a full-ROM `make` target.

## Build

```bash
cd "_wip/Ice Climber (U)/copilot"
make        # → cmp reconstructed_prg.bin prg.bin → "BYTE-IDENTICAL"
```

## Pass Status

| Pass | Status |
|------|--------|
| Pass 1 | **Complete** — 6,112 instructions, 12,230 bytes as code (74.6%), 4,154 bytes as data, byte accounting exact (16,384) |
| Pass 2 | **Not started** — 2 of 973 label definitions named (`Reset`, `NmiHandler`); 157 zero-page slots still neutral `ZpXX`; no Pass 2 map file exists |
| Pass 3 | Outstanding — data tables/structures unnamed |
| Promotion | Outstanding — add `header.s`/`chr.s` + HEADER/PRG/CHR `linker.cfg`, switch `make` to a whole-ROM `cmp`, move the `_tools` paths |

**Still owed:** a real power-on flow analysis (RESET/NMI/main-loop walk) in the style of the top-level project `OVERVIEW.md`s. This file was retitled and restatused in the 2026-10-19 doc-drift sweep to match the actual `prg.s`; that restatus was wrong and is corrected here.