Impossible Comeback

How it works

Every day there's a new endgame position, the same for everyone. You play Black and you're far behind – often a handful of discs against a board full of white. Yet the position is a proven win: with the right moves, Black finishes with more discs.

• The computer plays White perfectly. It solves the rest of the game exactly, so it never makes a mistake and always answers the same way.
• After each of your moves you see whether the win is still on. If a move lets it slip, that try ends, and you start again from the beginning. Your result shows how many tries you needed.
• Hints tell you how many of your moves keep the win. After 3 tries you can ask to see a winning move. Using help marks the day as solved with help.
• Difficulty rises through the week: Monday's puzzle is the gentlest and Sunday's the hardest. In every puzzle, only 1 or 2 of the first moves keep the win.

Why a comeback is possible

In Reversi the disc count can swing wildly in the last moves. What matters is mobility – having safe moves when your opponent has none – and getting the last move in each region of the board.

• Mobility
• Parity

Your streak

Solve the puzzle on consecutive days to build a streak. Your record stays in this browser if you allow Stats on this device in Cookie settings. It isn't sent to us.

Want a whole game?

Play the computer at 5 levels, from Beginner to Expert, or learn the basics step by step.

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