Claude - including Fable - was unable to solve this simple game from 1986 without my help. Is what it is.
A ROM-faithful model of The Sentinel (Geoff Crammond, Firebird, 1986) on the Commodore 64, plus a live driver that plays the real game in VICE (asid-vice) by keyboard and records an AVI. Transition primitives are validated byte-for-byte against the real 6502 code (golden fixtures, so CI proves them without the ROM); the enemy clock is gated frame-for-frame against the running game by the divergence instrument.
The phase player wins live, on the real game, verified by the ROM's own
landscape-complete flag ($0CDE bit 6) — including landscape 1442, which carries the
game's full complement of eight enemies (the Sentinel and seven sentries), in 29
actions, final energy 5:
pip install -r requirements.txt
pytest -n auto
python -m sentinel.phase_player 335 # offline, prints the action trace
python -m driver.play_player 335 # live in VICE, records an AVI
python -m driver.instrument 42 # race the model against the ROM, frame for frame
python -m driver.avi2apng renders/player_ls335_win.avi # the AVI as an embeddable APNG| landscape | enemies | offline | live |
|---|---|---|---|
| 0 | 1 | 29 | — |
| 42 | 2 | 32 | 36 actions (enemies frozen) |
| 60 | 7 | 44 | — |
| 110 | 3 | 35 | — |
| 298 | 7 | 36 | — |
| 321 | 7 | 28 | — |
| 335 | 7 | 60 | 66 actions |
| 373 | 7 | 32 | — |
| 1442 | 8 | 47 | 29 actions |
Offline counts are under the ROM-derived settle prices (sentinel/settlecost.py). The ls42
live entry is a driver.frozen_run win (update_enemies $16B5 RTS-stubbed): it verifies
frame-cost fidelity, not survival under fire.
Enemy counts include the Sentinel, so eight is the game's maximum. The ls1442 live run is recorded in full: media.md covers turning that AVI into the APNG above. A still from the ls335 win is here.
A landscape is identified by one number: the one a player types on the keypad. Every tool
here — driver.play_player, sentinel.phase_player, sentinel.player, sentinel.isoview
— takes exactly that number, and Game.typed(335) builds the same board offline.
| Area | Path | Role |
|---|---|---|
| Model | sentinel/ |
standalone forward model — terrain, LOS/aim, actions, energy, enemies, landscape generation (no emulator). Transition primitives are byte-for-byte against the 6502; see architecture.md for what is exact and what is not |
| Phase player | sentinel/phase_player.py |
the default player: freedom first, then convert. Wins all eight measured boards |
| Reactive player | sentinel/player.py |
tick-by-tick greedy player over the same BasePlayer |
| Landscape atlas | sentinel/atlas.py, sentinel/statecache.py |
per-landscape metrics (enemies, energy, terrain shape) over a cache of generated boards; --like matches one board to another |
| Driver | driver/ |
boot, enter a landscape, run memory-verified live keyboard operations (aim → fire → verify), record. Imports only sentinel/ |
| Instrument | driver/instrument.py, sentinel/statecmp.py |
frame-locked sim-vs-emulator divergence: seed the sim from the live image, step both one frame at a time, report the first disagreement |
The game is copyrighted and is not included. There is one supplied fixture: place
your own copy of the C64 tape image at sentinel-gold.tap.
out/sentinel_stage2.bin — the 64 KB memory image of the loaded game, used by the
oracle-marked tests that regenerate the goldens — is not a second supplied file: it is
generated from the tape. driver/dump_stage2.py boots the tape in asid-vice, dumps RAM,
and verifies the image by running the ROM's own generator against the model:
python -m driver.dump_stage2 # --out PATH, --force to re-dumpBoth files are gitignored; tests that need them auto-skip when absent. Generating the image
and running the live driver need Docker and the anarkiwi/asid-vice:latest image (build
from https://github.com/anarkiwi/asid-vice).
- gameplay.md — the game's rules and mechanics, ROM-derived spec.
- architecture.md — the landscape's geometry and the constraints it imposes, the game's state machines, one table mapping every ROM routine to its model function and validation, then the subsystems: landability filter, render-cost model, driver, instrument, measurement tooling.
- players.md — the phase player and the reactive greedy player: the rules that decide a move, the phases, current results.
- media.md — turning a recorded run into an embeddable APNG, and the blank test that drops the hyperspace and transfer frames.
- open_items.md — everything unsolved, and what was disproved.