Like poles push apart. That one fact from science class powers this neat deduction puzzle. Magnet Dominoes unblocked gives you a grid already split into grey dominoes and asks you to figure out which are magnets, which are plain, and which end of each magnet is plus.
James Harvey wrote it for Simon Tatham's Portable Puzzle Collection, where it goes by Magnets. Every puzzle is built to be solved by reasoning, without guessing.
How to play Magnet Dominoes
Each domino covers two squares. A magnet is charged plus on one half and minus on the other, while a blank domino is neutral on both. Numbers around the edge tell you how many plus poles and how many minus poles sit in each row and column. Plus counts run along the top and left, minus counts along the bottom and right.
There is one extra rule. Two matching poles can never touch side to side or top to bottom, so no plus next to a plus and no minus next to a minus. Neutral squares can sit next to anything.
Click a domino to drop in a magnet, and keep clicking to flip it or clear it. Right-click marks it blank, or tags it as definitely not blank when you know that much but not the direction. The Type menu offers different board sizes and difficulties.
Controls
| To… | Keyboard | Mouse | Touch |
|---|---|---|---|
| Place a magnet, flip it, then remove it | Arrow keys to move, then Enter (repeat to cycle) | Left-click a domino (repeat to cycle) | Tap a domino with Tap set to Magnet |
| Mark a blank domino, then "cannot be blank", then clear | Space (repeat to cycle) | Right-click a domino (repeat to cycle) | Press and hold, or set Tap to Blank domino and tap |
| Grey out a finished clue | — | Click the clue | Tap the clue |
| New game, undo, redo | N, U, R | Menu buttons above the grid | Menu buttons above the grid |
Tips
- Add a row's two clues. If plus plus minus equals the row length, every square there is charged and no domino crossing it is blank.
- Use the zeros. A row with no plus poles can only hold minus ends or blanks, which settles a lot of vertical dominoes.
- Spread outward from each magnet. A placed pole forbids the same pole next to it, so check the touching squares right away.
- Flat magnets come in pairs. A sideways magnet puts both of its poles in the same row, so uneven counts point to upright magnets.
- Grey out finished clues. Clicking a satisfied number dims it, so your eyes go only to rows that still need work.
Magnet Dominoes questions
What are the little question marks for?
They remind you that this piece is a magnet, even if you don't know which way it faces yet. The game doesn't check them, they just help you keep track.
How do I play on a touchscreen?
Tapping cycles a magnet through its two directions, and holding your finger down marks a blank. A small switch on the touch bar lets you swap what a tap does if you mark blanks more often.
Can blank squares touch magnets?
Yes. The no-touching rule only applies to matching poles. Neutral ends can sit beside a plus, a minus or another blank.
