Magnets

Each tile covers two squares. Fill each one with either a magnet (consisting of a + and − pole) or a neutral tile (green).

The clues are the numbers round the grid. The number of + poles in each row and column must match the clues along the top and left; the number of − poles must match the clues along the bottom and right. Two + poles may not be orthogonally adjacent to each other, and similarly two − poles.

Controls

On a touch screen, a tap does what a click does, and a long press what a right-click does (more ways to right-click).

Click a tile to make it a magnet, with the + in the end you click; click it again to turn the magnet round, and a third time to empty it. Right-click it to cycle it between empty, neutral, and a ? mark saying you’re sure it’s a magnet but don’t yet know which way round it goes. Keep the button down and drag to do the same to every tile you pass over that looked the same as the first.

With the keyboard, the arrow keys move a cursor around the board. Enter does what a click does to the tile under it, and Space what a right-click does.

A tile marked ? that lies along a row or column brings exactly one + and one − to that line, whichever way round it turns out, so it counts toward both of the line’s numbers.

Left-click on a clue to mark it as done (gray it out), and left-click it again to unmark it. Keep the left button down and drag to do the same to every clue you pass over that looked the same as the first. The keyboard’s cursor can step off the grid onto the clues, where Enter does the same.

Hints

Hint explains the next step rather than simply making it. It reasons only from the numbers, the tiles you have filled in and your ? marks, so it carries on from wherever you are, as long as none of those is wrong; if one is, it asks you to fix the highlighted mistakes first.

• A ring marks what the step decides: one end of a magnet, or a whole tile to make neutral or to mark ?.
• An outline marks what the step reasons from: the magnet a pole would touch (two of them are “like poles”), the tiles elsewhere in the line that can’t take the pole (“either outlined tile”), and the clues it reads. A clue a step counts with is recolored, and so is the clue of a line it only cites, because that line already has all its + or − poles: “its row’s clue”.
• Stripes mark the row or column the sentence calls “this row” or “this column”, running on through its numbers.

When a step says a tile must be a magnet but not which way round, it asks you for a ? mark: right-click the tile until the ? shows. Since a ? tile lying along a line brings one + and one − to it, the hint counts it toward both of the line’s numbers, and says “counting marked magnets” when a number is met only that way.

A few ideas are worth learning by name:

• Like poles repel. A pole can’t go beside the same pole, so a tile whose two ends both touch a + can’t be a magnet at all.
• A full line. Once a row has all its +s, no tile lying along it can be a magnet, and no other square in it can be +.
• No room to spare. When a line’s numbers need a + or − in every one of its empty squares, every tile there is a magnet; when they leave room for just one more neutral square, every tile lying along it is.
• The odd gap. When a line’s empty squares must all hold poles, they alternate. If the line needs one more + than −, the extra + comes from its one odd-length gap, which must start with +.

Magnets parameters

These parameters are available from the ‘Custom type…’ option on the ‘Type’ menu.

Width, Height

Size of the grid in squares. At least one of them must be 3 or more, or 5 or more for the harder of the two difficulties, which a 3x6 does not have either. Each must be between 2 and 61.

Difficulty

Determine the difficulty of the generated puzzle; see what the names mean.

Strip clues

Remove numbers from around the edge, one at a time, for as long as the puzzle still has only one solution at its difficulty. Some rows and columns then have no number for + or − at all.

More help

• Features every puzzle shares: hints, checking your work, checkpoints, playing by touch
• Help home