1Place a disc so it traps a line of enemy discs between it and another of yours.
2Every trapped disc flips to your side, and a move must flip at least one.
3If you have no move you pass; the game ends when neither player can move.
4Whoever has more discs at the end wins, and a corner disc can never be flipped back.
Questions
Have more discs showing your color than your opponent when the board is full or no more moves are possible. Count all discs when the game ends. The player with more discs of their color wins. If both have 32, it's a draw. Games are often decided by large margins since a single move can flip many discs.
Start with four discs in the center: two black and two white, arranged diagonally. Black typically moves first. Each player has a supply of discs (traditionally 32 each, sharing a pool of 64 two-sided discs).
Corners are extremely valuable - once captured, they can never be flipped. Prioritize corner control. Avoid placing discs adjacent to corners early, as this gives your opponent corner access. Edge squares (especially X-squares diagonally adjacent to corners) are dangerous early in the game.
The game originated in England in the 1880s as Reversi. In 1971, Japanese salesman Goro Hasegawa devised a version with a fixed starting position, launched in Japan in 1973, which became extremely popular worldwide.