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How to play
This page is the short version. The complete rules, with diagrams, examples and a glossary, are in docs/rules.md; inside the app, the Rules page shows them with live mini-boards.
- It's chess. Same board, same pieces, same moves, including castling, en passant and promotion.
- Capture the king to win. There is no check. The game warns you when your king is in danger, and if every move leaves a king to be captured for certain, that side has lost: its king cannot escape.
- Split a knight, bishop, rook or queen onto two empty squares: it becomes a ghost, 50 % on each.
- Merge the parts back together. Merging onto an enemy piece captures it, for certain when every part surely arrives.
- Land = roll, pass = link. Landing where a piece might be is settled by a fair roll: Captured, Moved or Missed, with the odds shown before you move. Sliding past such a square rolls nothing but links the pieces.
- Kings and pawns are always solid. Measure spends your turn to find out where one of your ghosts really is.
- Each side has a budget of 8 possible arrangements, so at most three 50/50 ghosts at a time.
| You see | It means |
|---|---|
| A normal piece | Solid: the piece is on that square for certain |
| A faded piece with a percentage | One part of a ghost: the piece is here with that chance |
| A dotted line between faded pieces | The parts of one piece |
| A thin thread with a chain icon | Linked pieces: where one is tells you where the other is |
| A ring around a king | King danger: the chance the opponent can capture it right now; red at 100 % |
| Pips next to a player's name | That side's quantum budget (0–8 used) |
Tap one part of a ghost for the what-if view: the board as it would be if that part is the real one.
| Move | What it does |
|---|---|
| Move | An ordinary chess move. If it lands where a piece might be, it is rolled. |
| Split | A knight, bishop, rook or queen goes to two empty squares at once and becomes a ghost. |
| Merge | Two parts of a ghost come together on one square. |
| Measure | Spend your turn to find out where one of your own ghosts really is. |
When a move lands on a square where a piece is or might be, and the result is uncertain, the game rolls. You see the odds before you move, and afterwards the result explains itself:
- Captured: your piece was there and took the other piece.
- Moved: your piece arrived; the other piece was not there.
- Missed: your piece was not really where it moved from, or its path was blocked. The turn still counts, and the board updates to what you learned.
Online, the server draws every roll at the moment the move is applied. In local games the same move in the same position always gets the same result, so undoing a move does not give you a new roll.