Reversi

The classic disc-flipping duel on an 8x8 board. Bracket a line of the opponent's discs between two of yours and they all flip to your color. The most discs at the end wins.

Rules

• Black moves first. A legal move places a disc on an empty square so that, in at least one straight line (horizontal, vertical, or diagonal), it brackets one or more opponent discs against another of your own. Every bracketed disc flips.
• You must play a flipping move if you have one. If you have none, you pass; if neither side can move, the game ends.

• Most discs wins. A 32-32 board is a draw (placement falls to the lower seat).

Writing a bot

You see the whole board, the scores, and whose turn it is. Return the square to play.

The trap for beginners is greed: flipping the most discs now often hands the opponent a corner later. Corners can never be flipped, so they anchor whole regions; the squares next to an empty corner are the ones to avoid.

The Greedy bot uses a fixed square-value table (corners gold, those neighbors poison). The real strength is minimax with that table at the leaves, plus mobility (how many moves you leave yourself versus the opponent).

Input and output

Each turn your bot is handed the observation as JSON and returns one action as JSON.

Observation: { "you", "to_move", "size", "board", "scores", "turn", "nonce" }. board[y][x] is -1 for empty, else the seat that owns the disc. Act only when to_move == you.

Action: { "x": <col>, "y": <row> }. The move must flip at least one disc. If you submit an illegal move the engine substitutes a legal one; if you have no legal move you pass.

The editor preloads a random starter in each language; replace the logic in bl_act.