The Story
Where it came from, and why it turned out this way.
OriginChina; a folk variant of xiangqi, popular in Fujian and Taiwan
Xiangqi pieces, an entirely different game
Banqi — also called dark chess or half chess — uses a complete set of thirty-two xiangqi pieces and yet has almost nothing to do with xiangqi. Only half the board is used, four files by eight ranks; all the pieces are laid face down at random to fill it; and movement, capture, and victory conditions are all rewritten. It is a classic folk variant: not designed but grown out of the circumstance of having one xiangqi set on hand, and especially popular in Fujian and Taiwan.
Even the sides are decided by a flip
The most distinctive rule is in the opening: whoever flips first gets whatever color they reveal, and their opponent takes the other. Before the first piece is turned over, neither player has a color and flipping is the only possible action. That places luck at the very front of the game and incidentally solves the first-move problem — you cannot plan a formation in advance, because you do not yet know which side you are.
The cannon is completely rewritten
The most interesting change is the cannon. It no longer captures by rank; it fires along a line over exactly one intervening piece to take whatever lies beyond, at any distance, up to and including the general. But when it is not capturing it moves only one square — no sliding as in xiangqi. That combination of enormous reach and terrible mobility makes the cannon a piece you must position in advance, and since face-down pieces can serve as screens, you never know whether the enemy cannon already has one lined up.
Flipping is itself a move
Each turn offers exactly two options: flip a face-down piece, or move one of your revealed pieces. Flipping looks like pure gambling but is in fact the most judgment-heavy action in the game — flip next to your own strong piece and you may hand your opponent an immediate capture; flip in a corner and the worst case is bounded. Strong players deduce the hidden pool from the revealed and captured pieces: while your opponent's general has not appeared, your soldiers retain their value.
- Soldiers capture the general while the general cannot capture soldiers; this cycle survives intact from xiangqi and is the most common way a losing position turns around.
- No piece may capture a face-down piece, which must be revealed first — but face-down pieces can serve as cannon screens. The two rules are frequently confused.
- The AI on this page never receives the true identity of face-down pieces; it sees only what has been revealed and captured, then searches across several possible distributions and aggregates.
Complete Rules
Start with what a turn allows and how the game is won.
- Board
- 4 × 8 squares
- Setup
- All 32 pieces face down
- Winning conditioncapture all of your opponent's pieces on the board and you win. The other losing condition is immobility — when no face-down pieces remain to flip and the player to move has no legal move at all, that player loses.
- At the start, all 32 pieces are shuffled and laid face down across the entire 4×8 board with no empty square anywhere. On your turn you have exactly two options: flip any face-down piece, or move one of your own already-revealed pieces.
- Sides are assigned by the first flip: whatever color the first player reveals becomes their side, and the second player automatically gets the other color. Before the first piece is revealed neither player has a color, and flipping is the only possible action.
- The ranking from highest to lowest is general, advisor, elephant, chariot, horse, cannon, soldier, and equal ranks may capture each other. Every piece except the cannon moves one square orthogonally per turn, either onto an empty square or onto an adjacent revealed enemy piece of rank no higher than its own.
- Soldiers and generals form a cycle: a soldier can capture only soldiers and the general, and cannot touch advisors, elephants, chariots, horses, or cannons; the general can capture advisors, elephants, chariots, horses, and cannons, but never a soldier.
- The cannon captures unlike anything else on the board: it ignores rank entirely and instead fires along a row or column, over exactly one intervening piece serving as a screen, to take a revealed enemy piece beyond it at any distance, including the general. Zero screens or two or more screens make the capture illegal, so a cannon can never take a piece directly beside it.
- When not capturing, the cannon may only step to one adjacent empty square — it cannot slide along lines like a xiangqi cannon. Its movement range is one square, exactly like any other piece.
- A face-down piece may serve as a screen but can never be a target. No piece may capture a face-down piece; it must be revealed first.
- Each color has 16 pieces1 general, 2 advisors, 2 elephants, 2 chariots, 2 horses, 2 cannons, and 5 soldiers.
Your First Game
Use this order of thought to get through a complete game quickly.
- Flip a corner square first. Corners have only two neighbors, so even if you reveal one of your opponent's strong pieces there, the number of directions from which it can immediately be captured is minimal.
- Before flipping, scan the cannon lines: for each of your revealed pieces, check its row and column for the pattern "enemy revealed cannon — exactly one piece — my piece." A face-down piece in the middle counts as a screen just the same.
- Memorize the two relationships that lose games: soldiers can capture the general but the general can never capture a soldier; and a cannon must have exactly one screen, so a piece pressed right up against a cannon is actually safe from it.
- Once you select a revealed piece of yours, the board shows only genuinely legal destinations and capture targets, including the cannon's long-range targets. Read those markers before committing.
- Do not flip repeatedly next to your own strong pieces. Reveal one of your opponent's big pieces there and they can capture the adjacent target on their very next move — the player who flipped has effectively given a piece away.
Practical Strategy
Move from knowing the rules to playing with a plan.
- Use the revealed pieces and the casualty list to track the pool of face-down pieces: each color has exactly one general, two cannons, and five soldiers. While your opponent's general has not appeared, your soldiers retain their value; only once all of your opponent's soldiers are dead is your own general truly safe.
- Until all of your opponent's cannons are gone, do not park chariots or horses on open lines, especially lines that already contain a piece that could serve as a screen.
- A cannon's value comes from an open long line plus a suitable screen, so sometimes preserving the intervening piece matters more than capturing it — once the screen is taken, the cannon cannot reach its target.
- When ahead, actively reduce the number of face-down pieces and simplify the position. When behind, do the opposite: keep face-down pieces around to create variance and wait to reveal a general or cannon that flips the material balance.
- In the endgame, controlling routes matters more than continuing to flip. Forcing your opponent to be the one who flips a dangerous face-down piece frequently wins both material and tempo outright.
Winning and Special Rules
Details that are easy to miss but can change the result.
- A player whose pieces are all captured from the board loses.
- When no face-down pieces remain and the player to move has no legal move at all, that player loses.
- Eighty consecutive moves — counting both sides' half-moves — with neither a flip nor a capture is a draw. Any flip or capture resets that counter to zero.
- The true identities of face-down pieces are never passed to the AI. The AI receives only the revealed pieces, the captured pieces, and the pool of remaining identities deduced from them, then searches several possible distributions of the hidden pieces and aggregates the results, rather than treating one random guess as the true board.
Common Mistakes
The traps new players fall into most often.
- Using the cannon like an ordinary piece and trying to capture an adjacent enemy — or treating two or more intervening pieces as a legal screen.
- Trying to capture a face-down piece with a cannon. A cannon's target must be a revealed enemy piece; face-down pieces can only be screens.
- Thinking in terms of a fixed side, forgetting that the first piece revealed is what decides who plays red and who plays black.
- Comparing ranks only and forgetting that soldiers capture the general while the general cannot capture soldiers — and parking your general next to an enemy soldier.