Twelve shapes made of five squares each, a combined area of sixty, and a set of rectangle puzzles with wildly different solution counts. Pentominoes started as recreation and turned into serious combinatorics.
A puzzle that slid apart easily in August can lock solid in January. The cause is equilibrium moisture content, and understanding it tells you what to do and what never to do about a seized puzzle.
Seven small polycube pieces, one three by three by three target, and 240 distinct ways to get there. Here is how the Soma cube works, where the count comes from, and why it is the right first polycube puzzle.
