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Frosted Board

Puzzle #18: Dots and Boxes

  • DifficultyMedium
  • To moveLight
  • TaskTake 12 of 16
  • Main line19 half-moves

Light to move on the 4 × 4 board. 21 of 40 lines are drawn, Dark has 0 boxes and Light 0.

16 boxes are still unclaimed. With best play you can take 12 of them, 8 more than the opponent gets, and exactly one line achieves that.

What the position is about

  • sacrifice — A piece is given up on purpose: the forced capture pulls the opponent onto the square you need.
  • split hand-out — Two boxes are offered so that they can only be taken one at a time, which keeps control.
  • open a chain — The right line opens a chain for the opponent at the smallest cost.
  • keep control — With best play you stay in control and collect more than half of what is left.

Finding the way in

Count the chains of three or more and the loops. If the count is wrong for you, look for a line that changes it, even at the cost of a box.

Before you touch a piece, list every forcing move you have and every threat the opponent has; the answer is almost always on that short list.

Show the first move

Start with a2-b2. Played out against the stiffest resistance, the whole line goes: a2-b2 a1-b1 a2-a3 c1-d1 c1-c2 b2-c2 c2-c3 c3-d3 c3-c4 b3-b4 a5-b5 a4-b4 d1-e1 d2-e2 d3-e3 d4-e4 d4-d5 c4-c5 b5-c5.

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.