QED Logic quod erat demonstrandum

Learn logic puzzles by understanding the reasoning, not just the answer

Play them yourself, watch them solved step by step, or get coached through every deduction. Every board is solved by logic alone: no guessing, no shortcuts.

Play it yourself

Solve a board on your own. Get hints that teach you the technique you are missing, not just the answer. Your rating grows as you improve.

Coach me

Work through a board step by step with the engine guiding you, explaining the reasoning behind every important move.

Walkthrough

Read the complete walkthrough: every move, every reason, written out so you can follow the logic yourself.

Every board is solved using eight named reasoning techniques, from basic single-cell placement to multi-step forced chains. Each technique is explained in plain language, so you build a mental toolkit you can apply to any puzzle.

Start with an 8x8 board. Work through one technique at a time. Come back when you are ready for the next.