Ninefall: a puzzle that proves its own solutions

Field notes

Ninefall’s central rule is that tile values add, roll over after nine, and trigger downhill cascades only through lower-numbered neighbours; equal values stop the chain. The homepage runs the same rules engine used by the game for an embedded sample level, with unlimited undo. Its level data records exact par solutions and optional goals, while the date-generated Daily Flip creates a shared five-by-five board without a server or account.