Reversi

Black moves first. Place a disc on an empty square so that one or more opposing discs lie in a straight line between your new disc and one already yours. Every bracketed line flips to your colour, horizontally, vertically or diagonally. Flips do not trigger further captures.

Dashed rings show legal moves on your turn. Select Legal moves to hide or show them. A solid dark disc is black; a pale disc with a dark outline is white. The small centre square marks the last placement.

If a player has no legal move, that player automatically passes. A player with a legal move must play. When neither side can move, the game ends, even if empty squares remain. More discs wins; equal counts draw.

Keyboard: Tab to the board. Arrows move between squares, Home/End move to a row’s ends, and Enter or Space places a disc. Each square’s label gives its coordinate, contents and legal capture count. Ctrl/Cmd+Z, or Undo turn, takes back your last move and the computer’s replies.

Choose black or white and a computer level. Changing either, or restarting, begins a fresh game and asks before replacing unfinished play. The computer opens when you choose white. Games resume in this browser when local saving works; undo history is reconstructed from the legal moves. No account or sync.

A legal move must capture at least one disc. The displayed legal moves are rule checks, not promises of strategically best play.

Corners cannot be flipped. Giving access to an empty corner is often costly; taking the most discs early can leave fewer choices later. Try comparing positions with Undo turn.

The original computer runs on this device in a browser Worker. Gentle, Steady and Deep use increasing search limits (up to 2, 4 and 6 plies). All have finite time and node budgets and may stop sooner; these names are local settings, not rated playing strength. If Workers fail, shorter local thinking keeps play available.

Rules reference: World Othello Federation. Reversi is this site’s working title. Code, artwork and explanations are original.