Logic Islands: Deduction Game

Logic Islands is a world of handcrafted deduction puzzles, built by a mathematician and a neuroscientist for people who like a real problem.

Not logic grids. Not another Sudoku clone. Not pattern-matching dressed up as a brain game. These are original deduction puzzles in the tradition of Raymond Smullyan's knights and knaves logical puzzles: islanders who can only tell the truth or only lie, and your job is to work out who is who from what they say. From there it gets stranger. You reason about what characters know, what they could have said, what the truth would have to be, and what questions you must ask.

Every puzzle is made by hand by a mathematician who has spent over a decade inventing them. No AI, not now, not ever. Each one was tested on hundreds of real people and refined until it was exactly hard enough, the progression exactly right. All explanations are handwritten too.

Ten islands, each with its own logic
You begin on the island of truth-tellers and liars. Beyond it lie nine more, each with its own residents, its own rules, and its own way of bending the truth. Enter a mysterious gallery of deceit, play the detective and weigh the reliability of up to eight witnesses in whodunits, and learn to ask the right questions of the right people, in the right order. The rules are taught through play, the difficulty climbs toward the genuinely mind-bending, and new islands keep arriving.

A fresh trio every day
Three new puzzles land each morning, separate from the island puzzles: a warmup, a challenge, and a master. Small enough to fit in a coffee break, but stimulating enough to stay with you all day. Keep your streak alive and climb the weekly and all-time leaderboards against everyone solving the same set.

Help at every step, never just the answer
Being stuck is part of it, but you are never stranded. Professor Logic gives a targeted nudge when you want one and a refresher on the idea in play. Once you solve a puzzle, he walks you through exactly why the answer holds. You come away understanding how to reason your way through even the most complicated problems.

Real reasoning, in the shape of a game
The skills here are the genuine article: the deductive reasoning used in mathematics and proof, relied on by anyone who has to think clearly under pressure, and tested on the LSAT and GRE. Propositional logic, knights and knaves, strategic questioning, reasoning about what others know, possibility and necessity, and more exotic logics. You'll learn to read AND, OR, XOR, IF-THEN, NOT, and a great deal more, as fluently as you read English. You will not feel like you are studying. You will just get sharper.

Who it's for
Puzzle solvers who have run out of things that truly challenge them. People who want more depth from their games. Anyone who loves paradoxes, proofs, or that satisfying moment when one detail forces every other piece into place. People who like a good argument and take pride in thinking things through. Mathematical, philosophical, and computing minds. Anyone preparing for the LSAT or GRE, or just looking to improve their logical reasoning skills. And anyone who misses the feeling of working something out entirely on their own, and wants to protect that.

Logic Islands is free to download. You get the first island and your first five days of daily trios free, no account required, no ads. When you want the rest, Logic Islands Pro opens every island, every daily puzzle, and every island still to come, plus personal analytics.

Think again.

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Recent changes:
Daily puzzles now count toward your leaderboard standing, smoother experience for returning users signing in with email to recover their progress on a new device, and there is a fresh round of fixes and polish throughout.