Reversi

Reversi is a two-player strategy game on a green eight by eight board. One player has the dark discs and the other the light ones. The game starts with four discs in the centre, two of each colour placed diagonally, and Dark always moves first. Play the computer at one of five levels, or pass one phone between two players.

How to play

• On your turn, place one disc on an empty square so that it traps a straight line of your opponent's discs between the new disc and another disc of yours. The line can run across, up and down, or diagonally.
• Every trapped disc flips over to your colour. One move can flip several lines at once.
• A move must flip at least one disc. If you have no such move, you pass and your opponent plays again. The dots on the board show where the side to move can play; you can switch them off in Setup.
• The game ends when neither player can move, usually because the board is full.

Scoring

Whoever has more discs on the board at the end wins. If the game ends with empty squares left, they are added to the winner's count, the usual way tournament games are scored, so a 40 to 20 finish with four empty squares is recorded as 44 to 20. A game where both sides have the same number of discs is a draw.

Strategy tips

• Take the corners. A disc in a corner can never be flipped, and it lets you build rows of safe discs along the edges.
• Be careful with the squares next to an empty corner, especially the diagonal one. Playing there often hands the corner to your opponent.
• Don't grab discs early. Having lots of discs in the middle of the game usually means fewer choices later. Aim to keep many moves for yourself and leave your opponent with few, bad ones. This is called mobility.
• Prefer quiet moves that flip few discs and stay away from empty squares, so you don't open new moves for the other side.
• Count near the end. In the last dozen moves, the exact number of discs flipped matters most.

Computer levels and saves

Rookie and Casual make plenty of mistakes and are good first opponents. Club looks a few moves ahead, Strong plays for corners and mobility, and Master searches deeply and plays the last fourteen moves perfectly. Undo takes you back to your last turn, and Hint shows the move the computer would choose. Your wins, best winning margin and streak for each level are saved in this browser, and an unfinished game is kept so you can close the tab and carry on later.