Logic puzzles on square and hexagonal grids, with a new game joining the collection regularly. Generated by mystify, an active research project: every level it ships is proven to have exactly one solution. And every hint comes from Demystify, an open-source solver running in your browser the whole time you play — if you're stuck, it works out the next deduction on the spot and shows you why.
Ready to play: each has a tutorial, a solver-grounded hint, and enough levels to stay for. Still beta — nothing here is polished, and we would like to hear what breaks.
Playable, and the hint works, but each is missing something — usually the tutorial. Dive in if you already like this kind of puzzle.
Tiny demos and failed experiments — sometimes a game doesn't work out! Kept here because they are more interesting to look at than to hide.
Combination came first, years before mystify — but its levels were generated too, by an earlier constraint-based system (Jefferson, Moncur & Petrie, SAC 2011). It was released on the iPhone and has long since vanished from the App Store; this is a modernised web version, playable again. The rest of the collection grew out of it.
It is the one game here with no Where? or Why? button. Those are driven by demystify, which explains a move by naming the clues that force it — and many Combination levels can be solved several ways, with interchangeable colours swapped throughout. Nothing is forced, so there is nothing honest to point at. The puzzles are unchanged; you are simply on your own.
Once a puzzle's rules are written in Essence, our constraint language, mystify does the rest: it generates levels, holds them to whatever “quality” means for that puzzle — no unneeded clues, no lucky guesses, no degenerate layouts — and sorts them by difficulty, each with exactly one solution and no problem-specific code. Different puzzles want different measures, and that is the point: the rules and the standards are both just constraints.
The GUIs here are built with the help of Claude Code; my research is puzzle design, not GUIs. More puzzles and more types are on the way.
The hints here aren't scripted. Demystify, an open-source solver that explains pen-and-paper puzzle deductions, is compiled to WebAssembly and runs in your browser the whole time you play. Press Where? or Why? and it solves your current board on the spot, finding the smallest set of clues that force the next step — the hint button isn't a workaround, it's the whole point.