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A pure-logic puzzle. The board is paved with domino slots; fill some with magnets — each a + end and a − end — and leave others blank, so that no two equal poles ever touch and the +/− counts on every row and column come out exactly right. Each board has one solution, reached by deduction alone.
Thick borders divide the board into domino-shaped slots, each covering two neighbouring cells. Every slot is either a magnet or blank. A magnet always has one positive (+) cell and one negative (−) cell; a blank slot leaves both of its cells empty.
Two rules decide everything. First, like poles repel: no + cell may sit directly next to another + cell, and no − next to another −, across slot borders (opposite poles touching is fine). Second, the clues — the red number by each row and column counts its + cells, and the blue number counts its − cells.
Tap a cell to cycle it through + , − , and empty; its partner in the same slot always takes the opposite, so setting one end sets the whole magnet. If you ever place two equal poles next to each other they glow to warn you. Get every row and column to match its red and blue clues with no clashes and the board is solved. There is always exactly one solution and no guessing is needed — your time is your score.
Start from the zero clues. A row or column whose + count is 0 can hold no + cell at all, and likewise for a 0 − count. That instantly fixes the orientation of any magnet poking into that line, and those forced poles cascade into their neighbours.
Full lines are just as powerful. If a line's + and − counts add up to its whole length, every cell there is a magnet (none blank), so you only have to work out which pole each one is — usually pinned down by the no-touching rule.
Use repulsion to chain deductions. The moment you place a +, every neighbouring cell across a border is barred from being +, which often forces those slots to be blank or to point their − end inward. Follow that ripple before guessing anything.
Don't forget blanks are a tool. Counting works both ways: if a line already has all the + and − it needs, every remaining slot touching it must be blank there. Marking those empties early shrinks the puzzle fast.