Play Magnets puzzle (Magnets) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Magnets is a logic puzzle on a grid already split into domino shapes. Each domino is either a magnet, with a + end and a - end, or a blank neutral piece. Numbers around the edge say how many + and - poles each row and column holds, and like poles may not sit side by side. The puzzle is ready below; start with the rows whose counts are smallest.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Place a magnet (+ on the clicked end), then flip it, then clear | Enter, repeated | Left-click a domino, repeated |
| Mark blank, then 'must be a magnet' (??), then clear | Space, repeated | Right-click a domino, repeated |
| Grey out a finished clue | - | Left-click the clue |
| Move the cursor | Arrow keys | - |
| Undo / redo | U or Ctrl+Z / R or Ctrl+R | Game menu |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Magnets is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
- Every domino is either a magnet (one + end and one - end) or blank (both ends neutral).
- The numbers at the top and left give the count of + poles in that column or row; the numbers at the bottom and right give the count of - poles.
- Two + poles may not be next to each other horizontally or vertically, and nor may two - poles. Neutral ends can sit next to anything.
Sizes and difficulty
The Type menu offers 6x5, 8x7 and 10x9 grids at Easy or Tricky, with some options marked as having stripped clues. Tricky needs more deductions about blank dominoes and the row and column counts. Stripped-clue puzzles leave some edge numbers out, which makes them harder. In Custom, a grid with an odd number of squares leaves one square blank; grids with an odd side tend to be easier.
Solving tips
A row or column with 0 for both + and - is all blank, so mark every domino crossing it. Once you place one pole, the squares beside it cannot hold the same sign, which often settles a neighbour's orientation. Use the ?? mark when you know a domino is a magnet but not which way round, then let the counts decide. A domino lying along a row puts one + and one - in that row if it is a magnet, which is handy for balancing counts.
Where this puzzle comes from
Magnets is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
What is the ?? mark for?
It is a note to yourself that a domino cannot be blank. The game ignores it when checking, but it lets you record that deduction before you know which end is + and which is -.
Can two magnets touch end to end?
Yes, as long as the touching ends are opposite poles, or one of them is neutral. Only + next to + and - next to - are forbidden.
Is Magnets free to play here?
Yes, with no limit on the number of puzzles. Magnets is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
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Want a game like this on your own site?
Magnets puzzle (Magnets) isn't ours to give away — we host it, we didn't write it. But eleven of the games here we did write from scratch, and those are free for anyone to put on their own page: one line of HTML, no account, no permission, no attribution beyond a credit line.