White moves first. The goal is checkmate: attack the enemy king so there is no legal escape. Every move must keep your own king safe. In computer mode, you play White.
One space. Four coordinates.
X is file a–d. Y is rank 1–4. Z selects the left or right board. W selects the bottom or top row of boards.
a1 [0,1] means a1 on Z = 0, W = 1: the top-left board. Moving from a1 [0,0] to a1 [0,1] changes only W.
Movement rules and practice lessons| Piece | How it moves | Try it |
|---|
| Rook | Exactly 1 axis · any distanceChange X, Y, Z, or W. A straight move can cross between boards. Pieces on the path block it. | |
|---|
| Bishop | Exactly 2 axes · equal distancesChange two coordinates equally: X + Y, X + W, or Z + W, for example. Not three or four. | |
|---|
| Knight | 2 steps + 1 step · jumpsMove two on one axis and one on another. The two-step part must be X or Y, because Z and W only run from 0 to 1. | |
|---|
| Queen | 1–4 axes · equal distancesChange any nonempty combination of coordinates equally. Unlike a rook plus bishop alone, this queen can also make three- and four-axis diagonals. | |
|---|
| King | 1 step · any combination of axesChange one or more coordinates by one. Never enter an attacked square, including attacks from another board. | |
|---|
| Pawn | Forward on Y · capture on Y + one other axisMove one empty rank toward 4 for White, or toward 1 for Black. Capture one rank forward plus one step on exactly one of X, Z, or W. Automatically become a queen on the final rank. | |
|---|
Checkmate means the king is in check and its side has no legal reply. A reply could move the king, capture a checker, or block a checking line. No legal moves without check is stalemate: a draw.
Blocking, check, and draws
Only knights jump. You cannot land on a friendly piece or leave your king in check. Crossing lines in the projection do not block a move unless the full X, Y, Z, W square is actually on its path. Kings are never captured.
There is no castling, en passant, or initial pawn double move. Each side starts with a king, queen, two rooks, one bishop, one knight, and four pawns. Draws are automatic on stalemate, the third occurrence of the same position with the same side to move, 100 half-moves without a pawn move or capture (50 moves per side), or two bare kings.
Inspect without making a move
Click any occupied square to inspect that piece, even your opponent’s. Green dots are playable destinations; blue diamonds are previews only. Rings mark captures. Clicking a capturable piece still inspects it and opens a separate capture confirmation. Use Inspect only to pause play and the computer. Opponent previews assume that side could move in the current position; they are not a prediction of its next turn.