Cờ Tướng9 × 10 · 32 pieces
Xiangqi rebuilt from the rules up: a real C++ engine, a board that floats, and nothing on screen that does not belong to the game.
01The stillness
Nine files, ten ranks, a river in the middle. The pond holds it, the lamp under the board lights it, and the water keeps moving while nothing else does.
02The pieces
A cannon needs a screen before it can take. A horse can be stopped at the knee. A soldier crosses the river and never walks back.
03The machine
Negamax with alpha–beta pruning, a transposition table, quiescence search and iterative deepening — candidate after candidate, until only one is left.
04The move
One of the oldest openings in the game — and the first one the engine will punish you for playing carelessly.
05Your move
Three difficulties, two players on one machine, or a room over the wire. The pond keeps moving either way.
01The rules, all of them
Each piece carries its own rule as a class in the engine — it knows where it may go and what blocks it. Legal moves come from the piece, not from a table of exceptions, so a new piece is a new class and nothing else changes.
Any distance along a rank or file, until something is in the way. The strongest piece on the board and the one that decides most endings.
Moves like a chariot, but captures only by leaping a single screen — one piece, friend or enemy, between it and the target. No screen, no capture.
One step straight, one step diagonally — unless a piece sits against its knee. The leg is blocked, and the move disappears.
Exactly two points diagonally, and never across the river. A piece on the midpoint closes the eye, and it stays at home for the whole game.
One point diagonally, inside the palace only. Two of them, and together they are the general's last wall.
One point orthogonally, inside the palace. The two generals may never face each other down an open file — that line is a weapon, and it wins games.
Forward, one point. After the river, sideways as well. Never backwards, never promoted — a soldier that reaches the last rank simply stays there.
02The engine
The same search runs at every difficulty; only its budget and its bookkeeping change. Easy is allowed to be careless on purpose. Hard is not.
| Level | Time | Depth | Technique |
|---|---|---|---|
| Easy | 0.1 s | 22 plies | Negamax + alpha–beta, 35% near-best choice |
| Normal | 0.5 s | 44 plies | + transposition table, quiescence search |
| Hard | 2.5 s | 88 plies | + iterative deepening, killer & history |
The same position reached by two move orders is searched once, keyed by a Zobrist hash. Half of the tree disappears.
At the depth limit it keeps capturing until the position calms down, so the score is not taken in the middle of an exchange.
It searches one ply, then two, then three — and keeps the best move from the last completed pass, so the clock is never the reason a move is lost.
03The world
A lotus platform that lifts and rocks on its own water, wet stone petals, spirit light in the shader and a five-tone score written in WebAudio. None of it touches a single rule.
04Play
In the browser
The same C++ engine, compiled to WebAssembly and served as static files. 28 MB, and nothing but the game once it has loaded.
Open the web buildWEB · WASM · 28 MB
Edge, Chrome, Firefox · WebGL 2
On the desktop
Electron shell, Chromium inside, the engine compiled natively. Unzip one folder and run Xiangqi.exe — no toolchain, no Node, no browser.
Download for WindowsWINDOWS 10 / 11 · x64 · 282 MB
Unsigned student build · SmartScreen may warn
Over the wire
Online play runs on a Cloudflare Durable Object that holds the board and the clock, so both clients see the same legal move or the same rejection.
WSS · one live session per room
In a terminal
The same engine, no graphics, one binary. Useful for reading the search and for proving the rules are real.
C++17 · POSIX terminal
make console && ./bin/cotuong