What Is a Mechanical Puzzle? Parts, Kinds and Why They Get Hard
A mechanical puzzle is an object you solve by moving or fitting its parts. Its parts, kinds, rules and why half of a sliding tray's positions are unreachable.
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Articles about peg solitaire
Why Some Peg Solitaire Puzzles Are Unsolvable
A colouring trick shows why some peg solitaire puzzles can never end with one peg, and what research found about symmetric and unique-solution boards.