Knights & Knaves Puzzles

Knights and knaves puzzles come from a format popularized by logician Raymond Smullyan: on this island, every islander is either a knight, who always tells the truth, or a knave, who always lies. You're given a handful of statements — often islanders talking about each other — and have to work out who's a knight and who's a knave from what's consistent.

Every knights-and-knaves puzzle here is checked by a constraint solver before it's published, which tries every possible assignment of knight/knave and confirms exactly one is consistent with every statement. The ∎ verified badge means that check ran and passed, not that we think the puzzle reads well.