Skip to content
Frosted Board

Puzzle #29: Reversi

  • DifficultyHard
  • To moveLight
  • TaskOnly winning move
  • Main line12 half-moves

Light to move. There are 15 dark and 38 light discs on the board and 11 empty squares.

You have 6 legal moves and only one of them keeps the ending won: with perfect play on both sides it finishes 38–26. Each of the 5 alternatives was searched to the last disc and draws or loses.

What the position is about

  • a pass in the line — Somewhere in the main line one side has no move and must pass.
  • edge square — The key move is on the edge of the board, where discs are harder to flip.
  • only winning move — Every legal move was solved to the end: this one wins, all the others draw or lose.

Finding the way in

Eleven empties are too many to guess. Start with the moves that take away the opponent's options or force a pass, and check whether the corner you are tempted by really holds.

Take your time. There is no clock on the result, and a wrong move is simply taken back so you can look again.

Show the first move

Start with g8. Played out against the stiffest resistance, the whole line goes: g8 e1 a1 g3 a6 a5 a4 b3 a3 g1 -- a2.

Solve it and the next puzzle of the same game is one tap away. Your solved puzzles are ticked in the list, in this browser only.