The explosion
What goes. The capturing piece, the captured piece, and every piece on the four points orthogonally next to the capture point, whichever side they belong to.
What stays. Diagonal neighbours. Soldiers: an explosion never removes a soldier, so a soldier leaves the board only by being captured itself, though a soldier that captures explodes like anything else.
Your general. You cannot capture next to your own general; the blast would take it. So a general never captures.
Their general. A capture next to the enemy general wins on the spot. The advisors beside each general are the points the game turns on.
The cannon shot is the one exception
A cannon’s capture does not explode. It removes only the cannon and its target: nothing beside the target is touched, and neither is the screen the cannon fired over. The shot is at range; the explosion is on contact.
This is the one change from a straight port, and it is there because the straight port has a draw by repetition that can start on move three and that the defender can never refuse. A chariot on the file of an advisor threatens to blow up the general. The only defence is to block with a cannon, and with cannons exploding, the block is also a shot back over the chariot at the attacker’s own advisor, so the chariot has to move to the other advisor file, the cannon follows, and the position repeats. In engine games a side that had lost a chariot could hold the draw this way against a far stronger opponent. A quiet shot leaves the block standing but harmless, and the check rule below makes the hop that remains a loss for the side making it. The cannon becomes a piece you trade and block with rather than the piece that clears a rank, and everything else about the explosion stays as it is.
A threat to blow up the general is check
Xiangqi’s rules about the general stand. A move may not leave your general where a piece attacks it, and the two generals may not face each other down an open file. Checkmate wins. A player with no legal move loses.
One thing is wider than in xiangqi. Your general is in check whenever the opponent could remove it with their next move, and under these rules that includes taking the piece beside it. A chariot bearing on your advisor is bearing on your general. The board shows this as check, and it matters for the repetition rule below: a player who gives this kind of check on every move of a repeated cycle loses, as a player giving ordinary perpetual check does under xiangqi’s tournament rules.
How games end
You win by blowing up the enemy general, by checkmate, by leaving the opponent with no legal move, or when the opponent gives perpetual check in the wide sense above. Games also end by timeout, resignation, or abandonment, the same as any other game here.
Two rules draw. Sixty consecutive plies without a capture is a draw, the same limit as xiangqi here. The third occurrence of the same position is a draw, unless one side gave check on every move of the repeated cycle: then that side loses, where plain xiangqi on Mistboard would call it a draw. If both sides did, it is a draw.
A sample game
One of the engine games behind this page: Fairy-Stockfish at ten million nodes as Red against itself at one million. Red is a pawn and a half up by move 6 and the game stays close until Black’s 21…Hxf9, a horse taking a cannon on f9 with Black’s own advisor on f10 beside it. The blast takes the advisor, the palace is a piece lighter for nothing, and it never recovers: 30…Cb9 leaves the general without cover, and on move 38 Red’s chariot takes the cannon on d8, next to the general on d9. The blast takes the general, and the elephant on e8 with it.
Where to next
Play it against the engine at any of eight strengths, or against a friend with an invite link. The launch note is what decides a first game; the design post has the measurements behind the cannon rule; the study has all twelve engine games, with every explosion marked and a note on the move that decided each.