Reversi

How to win at Reversi

The biggest surprise for new Reversi players is that flipping the most discs early is usually a losing strategy. Because every disc can be flipped again and again until the board fills, an early lead means almost nothing. What matters is who controls the board on the final move. The real currency is mobility: the number of legal moves you have available. If you can keep your own options open while shrinking your opponent's, you will eventually force them into bad, self-damaging moves. Aim to hold a small, well-placed cluster in the opening rather than a fat pile of flippable discs in the center.

Strong players talk about the frontier: the set of your discs that touch empty squares. Every frontier disc is a target waiting to be flanked, so a sprawling frontier hands the opponent safe flips all game long. Othello theory even has a name for keeping your disc count deliberately tiny, evaporation, and it works because a player with few discs usually has few weaknesses and plenty of moves. On Inkplay you play the light discs and move first, with every legal square marked by a dot. Treat that dot count as a health bar: when it shrinks toward two or three while the computer keeps six or seven, trouble is already here no matter what the disc totals say.

Corners, X-squares, and C-squares

A disc becomes permanent, or stable, once it can never be flanked again, and corners are the only squares that are stable the instant you play them. That makes the four corners the most valuable real estate on the board. The squares around them have names too: the X-square touches a corner diagonally, and the two C-squares sit beside it along the edges. Playing an X-square while its corner is empty is the most reliable way to lose a game of Reversi, because it opens the diagonal and invites the opponent to land in the corner and grow a stable wall out of it.

• Take corners whenever you safely can. They anchor whole edges and can never be flipped back.
• Avoid X-squares next to empty corners at almost any cost, and treat C-squares with nearly the same suspicion.
• Prize mobility: keep several legal moves for yourself while forcing the computer toward having none.
• Play quiet, inward moves early so you do not build a big, exposed frontier of flippable discs.
• Watch for skipped turns: if the computer has no legal move, you get to move again.

The greedy-move mistake

Most losses come from grabbing a big flip in the first twenty moves. Here is the pattern in miniature: you flip six discs along a diagonal and feel great. Next turn you discover the computer has three new replies through the wall you just built, while your own dot count has dropped to two. A couple of moves later you are the one forced to hand over an X-square, and the corner follows. That pile of your color sits in the middle where the opponent can flank it and reclaim everything, and worse, it used up the safe interior moves you needed to stay flexible. Think of the midgame as maneuvering instead: give up discs freely when it keeps your opponent short of good options, and cash in only in the closing moves, when flips finally become permanent and the count actually sticks.

Parity: the endgame edge

Once the board splits into pockets of empty squares, start counting them. Whoever plays last in a region usually flips discs nobody can answer, so you want each pocket to hold an even number of empties when the opponent is due to enter it, leaving the final play there for you. This idea is called parity, and it explains a habit that looks eccentric in strong players: passing up a juicy flip to drop a quiet stone into a different corner of the board. They are rearranging who moves last where. In the final ten moves, stop thinking about mobility entirely and just count the finishing discs for each candidate move. A modest move that seals an edge often beats a flashy flip through the middle that the very next reply reverses.

Reversi and Othello

Reversi was first sold in England in the 1880s, with rival inventors Lewis Waterman and John Mollett both claiming to have devised it, a feud carried out in the pages of Victorian games magazines. In 1971 the Japanese businessman Goro Hasegawa refined and trademarked a version called Othello, named for the Shakespeare play, its black-and-white discs echoing the drama's themes. Launched in Japan in 1973, it became a nationwide craze, and the World Othello Championship has run every year since 1977. The rules are essentially identical to Reversi; Othello simply fixes the standard four-disc starting position in the center. Computers passed the best humans long ago: in 1997 the program Logistello beat world champion Takeshi Murakami six games to nil, and modern engines are effectively perfect. None of which matters at the human level, where the player who respects corners, mobility, and parity beats the one who chases flips almost every time.