Reversi rules: legal moves, passing and corner decisions
Reversi turns a single placement into several possible captures. Learning to close a line is the first step; understanding the moves you leave your opponent is the next. A lead in discs is only a position, not a final result.
A move must bracket an opposing line
The 8×8 board begins with two black and two white discs diagonally arranged in the centre. Black moves first. Place one disc on an empty square so that a continuous line of opposing discs lies between it and an existing disc of your colour.
Check horizontal, vertical and diagonal directions. A gap breaks the line, and you cannot skip a friendly disc to capture beyond it. New black → white → white → black flips both white discs. Replacing either middle disc with an empty square prevents that capture.
One placement can capture several directions
Every opposing line bracketed by the placement must flip. You cannot choose to leave a legal line untouched. The engine checks from the newly occupied square; the flipped discs do not start a chain reaction of further captures.
A highlighted legal square tells you that at least one capture exists, not that the move is best. Trace each direction before playing, then look at the new empty squares your opponent will be able to use.
Why the same player sometimes moves twice
Passing is compulsory when no legal move exists and forbidden when one does. Our game handles it automatically. Having no move on one turn is not an immediate loss: a later opposing placement may create a legal response.
The game ends when neither player can move. Empty squares may remain. Count the discs of each colour: the larger total wins and equal totals draw. Board completion is therefore sufficient for an ending, but it is not required.
Do not confuse a large capture with a strong position
A corner cannot be bracketed from beyond the board, so a disc placed there stays stable. Squares beside an empty corner deserve care because a reply may give that corner away. Check the actual reply rather than treating every edge move as safe.
Compare the opponent's available choices after candidate moves. Restricting those choices can matter more than the immediate disc gain, but it is not a universal winning formula. In the endgame, count and examine the remaining moves instead of following an opening slogan.
Use the browser edition to review a position
Play against three computer difficulties or share one device with another player. Local two-player mode is not an online match room. Progress and statistics stay in the current browser; they do not certify a global ranking.
Click or tap a legal square, or navigate with the keyboard and confirm. Hints and undo support review during an active game. Changing the mode or difficulty starts a new game, so finish examining a position before making that change.
Keep playing
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