TECHNIQUE 3 OF 4
Mobility: count and inspect the opponent's choices
A large immediate capture can leave the opponent many good replies. Compare the legal moves available after a candidate placement, including the quality of those moves rather than only their number.
The rule and its limit
For each candidate, apply all required flips and enumerate the opponent's legal placements on the resulting board. Reducing that set can constrain their choices, but the count is a heuristic, not a complete evaluation. One remaining reply may be an excellent corner move, while several alternatives may all be less useful.
A common mistake
Maximising discs taken now confuses current score with final score. Minimising the opponent's move count mechanically is another shortcut that can ignore the value of their remaining reply.
PLAYABLE EXAMPLE 1
More flips can leave more replies
Violet to move. Compare immediate flips with the number of legal replies you leave the opponent. Which move leaves the fewest replies? Does the largest capture always do that here?
Loading playable study…
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.
Compare the starting moves
The fewest opposing replies is 5, after R2C3. At least one maximum-capture move leaves more replies. Fewer replies is a position feature to compare, not a proof of best play or victory.
| First move | Immediate effect | Checked consequence |
|---|---|---|
| R1C2 | Flips 2: R2C2, R3C2. | Opponent has 8 legal replies, including corner R1C1. |
| R1C6 | Flips 2: R2C5, R3C4. | Opponent has 8 legal replies. |
| R2C1 | Flips 1: R3C2. | Opponent has 7 legal replies. |
| R2C3 | Flips 2: R3C2, R3C3. | Opponent has 5 legal replies. |
| R3C6 | Flips 1: R2C5. | Opponent has 10 legal replies, including corner R1C6. |
| R4C5 | Flips 1: R4C4. | Opponent has 10 legal replies. |
| R4C6 | Flips 1: R3C5. | Opponent has 9 legal replies. |
| R5C4 | Flips 2: R4C4, R3C4. | Opponent has 9 legal replies. |
| R6C5 | Flips 1: R6C4. | Opponent has 7 legal replies. |
PLAYABLE EXAMPLE 2
Count choices as well as discs
Cream to move. Compare immediate flips with the number of legal replies you leave the opponent. Which move leaves the fewest replies? Does the largest capture always do that here?
Loading playable study…
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.
Compare the starting moves
The fewest opposing replies is 7, after R1C5, R5C4. At least one maximum-capture move leaves more replies. Fewer replies is a position feature to compare, not a proof of best play or victory.
| First move | Immediate effect | Checked consequence |
|---|---|---|
| R1C3 | Flips 1: R2C4. | Opponent has 8 legal replies, including corners R1C1, R1C6. |
| R1C5 | Flips 1: R2C4. | Opponent has 7 legal replies, including corners R1C1, R1C6. |
| R2C3 | Flips 1: R2C4. | Opponent has 8 legal replies, including corners R1C1, R1C6. |
| R3C1 | Flips 2: R4C2, R5C3. | Opponent has 10 legal replies, including corners R1C1, R1C6. |
| R5C1 | Flips 1: R4C2. | Opponent has 10 legal replies, including corners R1C1, R1C6, R6C1. |
| R5C2 | Flips 2: R4C2, R4C3. | Opponent has 8 legal replies, including corner R1C1. |
| R5C4 | Flips 2: R4C3, R4C4. | Opponent has 7 legal replies. |
| R5C5 | Flips 2: R4C4, R4C5. | Opponent has 8 legal replies, including corner R1C6. |
| R5C6 | Flips 1: R4C5. | Opponent has 8 legal replies, including corners R1C1, R1C6. |
| R6C2 | Flips 3: R5C3, R4C4, R6C3. | Opponent has 8 legal replies, including corner R1C6. |
Equal reply counts can hide different corner access
Use playable example 2 above (study reversi-06). From its starting board, compare Cream placing at R1C5 with Cream placing at R5C4. Both moves leave Violet seven legal replies.
The tempting move
Treat the moves as equivalent because the opponent has seven replies after either one.
Why it fails
After R1C5, Violet can reply at either R1C1 or R1C6: both are corners. After R5C4, none of Violet’s seven legal replies is a corner. The equal count conceals a concrete difference in the available squares.
What you can conclude
R5C4 denies an immediate corner reply in this position, while R1C5 permits two. That is more information than the reply count alone provides. It still does not prove the best full-game move or eventual winner. Reset example 2 before comparing the two branches.
Try the idea in another position
Two legal candidate moves have been checked. Move A flips five discs and leaves the opponent seven legal moves. Move B flips one disc and leaves two legal moves. What is proved by these counts, and what is not?
Check your reasoning
B leaves fewer legal replies than A, while A captures more discs immediately. Neither fact proves which move wins or is best. Inspect the actual replies, especially corner access and further consequences, before making a stronger strategic claim.