Reversi Strategy: Corners and Mobility

Reversi rewards restraint. Flipping the most discs now often gives your opponent more choices, while a quiet move that controls an edge can decide the final count.

Corners cannot be flipped

A disc in a corner is permanent because no line can extend beyond it. From there, you can often secure more discs along both adjoining edges.

Treat the three squares beside an empty corner with care. The diagonal X-square is especially dangerous: occupying it often lets your opponent take the corner on their next move.

Play for mobility, not the early count

Mobility is the number of legal moves available. Prefer moves that leave you several choices while cutting down your opponent’s options. A move that flips one disc can be stronger than one that flips six.

If your opponent has no legal move, their turn passes and you move again. Building toward a forced pass can give you control of a whole region.

Keep frontier discs low

A frontier disc touches at least one empty square. Frontier discs give your opponent handles to capture, so having fewer of them usually makes your position harder to attack.

Avoid spreading across every open edge early. Compact groups inside the position often preserve more safe moves.

Use parity in the final empty regions

Near the end, empty squares split into regions. Taking the last move in a region is often valuable because it can force the opponent to open the next one. With an even number of empties, think about whether a pass changes who gets that last move.

Parity is a guide rather than a rule: corners and forced moves still matter more.

Count the exact endgame

When only a few squares remain, stop judging by appearance and calculate each legal sequence. Include automatic passes: a line that looks one move shorter may give the same player two placements in a row.

The game ends when neither player can move, even if empty squares remain. Count the final Black and White discs; the larger total wins and equal totals draw. Hard practice searches these small endgames to the finish.

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