About Reversi
Reversi is a game of outflanking: every disc you place must trap a line of your opponent's discs, which then flip to your colour. You play black against a computer that favours corners and edges, and the lead can swing wildly right up to the final move.
How to play
- The board is 8x8 and starts with four discs in the centre, two black and two white placed diagonally. You play black and move first.
- A legal move places a disc on an empty square so that one or more straight lines of white discs lie between it and another black disc, in any of the eight directions.
- Every white disc trapped in those lines is flipped to black. Moves that flip nothing are not allowed.
- If a player has no legal move, they pass automatically and the other player moves again.
- The game ends when neither side can move. Whoever has more discs on the board wins; equal counts are a draw.
- If you win, the number of black discs on the board is submitted as your score. A loss scores 0.
Controls
- Click or tap a square to place a disc. Small dots mark every square where you can legally play.
- Squares are buttons, so Tab and Enter or Space also work.
- The score bar shows the current disc count for both sides.
Tips and strategy
- Corners can never be flipped, so a corner disc is permanent. Getting them is usually worth more than any number of flips in the middle.
- Be wary of the squares diagonally next to an empty corner. Playing there often hands the corner to your opponent; the computer itself avoids them.
- Do not chase disc count early. Having fewer discs in the opening often means having more options later, while your opponent runs short of moves.
- Try to limit your opponent's legal moves. Forcing a pass, or forcing a bad move near a corner, wins more games than big flips.
- Edges are stable once anchored to a corner. Build along edges from a corner you own rather than from the middle of an empty edge.
Background
Reversi was developed in England in the 1880s, with Lewis Waterman and John W. Mollett both claiming to have invented it. In the 1970s a version with a fixed starting position was marketed in Japan under the name Othello by Goro Hasegawa, and that version became the basis of international tournament play. The starting position used here, with the four centre discs placed diagonally and black to move, matches the Othello setup.
Questions
- How strong is the computer?
- It uses a weighted board that prizes corners and edges and penalises the squares next to corners, plus a one-move check of your best reply. It plays sensibly but does not search deeply, so solid positional play can beat it.
- What happens if I have no legal move?
- The game says you pass and hands the turn to the computer automatically. If neither side can move, the game ends.
- Can the game end before the board is full?
- Yes. It ends as soon as neither player has a legal move, even if some squares are still empty.