How to play
Reversi is played on an 8 × 8 board that starts with two black and two white discs in the centre. Black moves first. Place a disc so that a straight line of your opponent’s discs — across, down or diagonally — is sandwiched between it and another of your discs; every disc in that line flips to your colour. Each move flips at least one disc. When you have no legal move your turn passes, and when neither side can move the game ends and the player with more discs wins. Tap a square to play; the small dots show where you can move, and Undo takes back your last move.
Computer levels
Easy plays mostly at random. Normal picks the move that looks best right now and loves corners. Hard reads four moves ahead with alpha-beta search and calculates the last few moves of the game exactly. Wins are counted separately for each level and saved in this browser.
Tips
A disc in a corner can never be flipped, which makes corners the most valuable squares. While a corner is still empty, play away from the square diagonally next to it so your opponent can’t reach the corner. Early on, flipping fewer discs is often stronger: it keeps your own options open and leaves your opponent fewer places to move.