Yin-Yang Font: G4G Puzzle

Can you fill in every empty square with either a black or white circle so that the black circles are orthogonally connected together, the white circles are orthogonally connected together, and no 2 × 2 square is all black or all white? This puzzle is a full-word puzzle based on the Yin-Yang font, and was featured as part of a G4G14 presentation. See the font page for a description of how we generated the puzzle.

You can interactively solve the puzzle by clicking on the blank spaces. Left clicking (or touching) toggles between black, white, and blank. Right clicking acts as an eraser. Middle clicking toggles between black and white, or fills in white. You can drag to paint many circles at once. If you make any local mistakes, they will highlight red: 2 × 2 squares that are all the same color (invalid by the rules) or that alternate black/white/black/white (a derived rule because it makes connectivity impossible — see our paper).

Check out other mathematical and puzzle fonts. • Feedback or not working? Email Erik. • Source code on GitHub.