game-solver
A retrograde-analysis engine for small combinatorial games, the WASM build of it, and a browser explorer that plays perfectly against the tablebases it produces.
The engine enumerates a game's reachable positions, works backward from the terminal ones, and propagates win/loss/draw until every position has an exact value. Cyclic games (where positions repeat) are handled by a reachable-graph solver rather than plain backward induction, which is what makes the morris family tractable.
▶ Open the explorer
Results
| Game | Result under perfect play | Positions | Notes |
|---|
| Six men's morris | Draw | 42,372,745 | No earlier published solution found (searched 2026-10-17) |
| Six men's morris (flying) | Draw | 42,383,945 | |
| Five men's morris | Draw | 17,844,721 | |
| Four men's morris | Draw | 4,111,151 | |
| Three men's morris | First player wins | — | Classical folklore; reproduced here |
| Y (side 6) | First player wins | — | Solved slice-by-slice to fit in memory |
| Tic-tac-toe | Draw | — | Validation target |
No published solution of six men's morris was found in the academic work (Gasser 1993; Gévay and Danner 2014), in the open-source solvers Malom and Sanmill, which cover nine, twelve and Lasker morris plus Morabaraba but not six, or in a web search on 2026-10-17. Unpublished and non-English work was not searched. The tablebases are published so the result can be checked rather than believed.
Tablebases: tablebase-v1 release — .wld files with a .meta.json each giving the encoding and the win/loss/draw breakdown.
Write-up: Six Men's Morris Is a Draw.
Layout
engine/ Rust solver. One module per game under src/games/, binaries under src/bin/.
wasm/ wasm-bindgen wrapper exposing the engine to the browser.
explorer/ Vite app. Queries the tablebases client-side; no server.
Build
The engine is a plain Cargo project:
cd engine && cargo test && cargo run --release --bin morris_tablebase
The explorer depends on the WASM build via a file: path, so build that first:
cd wasm && wasm-pack build --target bundler
cd ../explorer && npm install && npm run build
Tablebases land in engine/artifacts/ and are gitignored; they ship as release assets.
Provenance
This engine began inside solved-games, a reference registry of solved games, as a way to verify the records rather than take them on faith. It outgrew that role within a day and was split out here with its history intact. The commit that solved six men's morris is preserved with its original date.
Licence
MIT. See LICENSE.
