DECISION STUDY · reversi-04
Compare a corner with a larger field
Violet to move. Which legal moves occupy a corner? Compare them with a non-corner capture and identify any corner replies you would give away.
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Select a legal empty square. Violet (V) and Cream (C) are the two players. You control both sides here. Bracketed discs flip automatically; a player without a move passes automatically.
Keyboard: Tab to an enabled control, then press Enter or Space. The study starts from the diagram shown; reload can restore your own saved moves.
Try the task before inspecting the answer.
Show the starting-position answer and evidence
Legal corner moves: R1C6. A corner cannot subsequently be bracketed, so the corner disc is stable. That fact alone does not prove a full-game win.
| First move | Immediate effect | Checked consequence |
|---|---|---|
| R1C6 | Flips 1: R2C5. | Opponent has 5 legal replies. |
| R2C1 | Flips 1: R3C2. | Opponent has 6 legal replies. |
| R2C3 | Flips 1: R3C3. | Opponent has 5 legal replies. |
| R3C1 | Flips 3: R3C2, R3C3, R4C2. | Opponent has 4 legal replies. |
| R3C5 | Flips 1: R4C4. | Opponent has 8 legal replies. |
| R3C6 | Flips 1: R2C5. | Opponent has 6 legal replies. |
| R4C1 | Flips 1: R4C2. | Opponent has 8 legal replies. |
| R4C5 | Flips 1: R4C4. | Opponent has 8 legal replies. |
| R5C1 | Flips 2: R4C2, R3C3. | Opponent has 7 legal replies. |
| R5C4 | Flips 1: R4C4. | Opponent has 8 legal replies. |
| R6C5 | Flips 1: R6C4. | Opponent has 6 legal replies. |
How this position was checked
Reached by the recorded legal moves from the six-by-six opening, including any automatic passes.
Reproduce from the regular starting board: R3C2, R4C2, R5C3, R2C4, R2C5, R6C4, R6C3, R2C6, R1C4, R2C2. Follow automatic passes when they occur.
Explain what you learned
Choose one first move from the comparison table. Explain its effect without rereading the answer. Then change the first move and identify which part of the explanation changes. These comparisons answer the stated task from this starting position. They do not prove the best move or eventual winner in a different position.
Rules and limits
Playfield's classic Reversi uses a six-by-six board with four starting centre discs. Violet moves first and alternates with Cream when both have legal moves. A placement must bracket one or more consecutive opposing discs between the new disc and an existing friendly disc in at least one of eight directions. Every bracketed line flips. The interface automatically passes a player with no legal move. The game ends when neither player can move, even with empty squares left; the greater disc count wins and equal counts draw. All discs count equally in this version.
Capture legality, legal-move counts, corner stability, passes and final counts can be checked exactly. Mobility and avoiding access to an empty corner are strategic considerations, not universal winning rules. More legal moves, more current discs or ownership of a corner does not alone prove a final win. The regular game is local two-player play; example analysis is not an unannounced computer opponent or a claim of perfect strategy.