Lights Out
Turn every light off. Explore 3×3 to 7×7 boards, difficulty levels, hints, and a GF(2) solver.
Open experiment ↗Labs
Logic games and probability experiments.
Four Colour
Colour a map so adjacent regions never share a colour. Switch between map and graph views.
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Peaceable Queens
Place balanced groups of white and black queens so neither colour attacks the other.
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Royal Cards
Arrange 16 cards so every row and column contains each face and suit exactly once.
Open experiment ↗Penney’s Game
Choose two three-flip patterns. Race them across five independent 100-flip sequences.
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