A daily deduction puzzle on a nautical chart. One hex on today's island is drawn as something it is not. Every survey note is true, and only one hex can satisfy them all. Find it and file your correction; you get three. New since our first launch: the Android app, spoiler-free share cards with a beat-my-time challenge, and Google sign-in. Casual and Standard charts are free in any browser, no account needed. Hard and Fiendish, streaks, ratings and duels live in the iOS and Android apps.

Somewhere on today's map, one hex is drawn as something it is not. You get four survey notes, and every one of them is true. Only one hex can satisfy all four at once; that hex is the liar. "The lie touches exactly 0 reefs." "The lie is drawn on reef or heath." Put those together and every reef is dead. You are not guessing, you are proving. One map a day, the same one for everyone, about three minutes. Free in the browser, no account.