Magnets

What is Magnets?

Magnets is a logic puzzle played on a square board tiled with dominoes. Every domino is either a magnet, with a + pole at one end and a − pole at the other, or a neutral blank. The numbers along the top and the left of the board say how many + each column and row holds, and the numbers along the bottom and the right count the −. Two equal poles may never sit side by side in a row or a column, though they may meet corner to corner.

Every board has exactly one answer, and it can always be reached by reasoning, never by guessing. Boards come in three sizes, 6 by 6, 8 by 8 and 10 by 10, and a new board, the same for everyone, arrives every day.

How to play

Tap a cell to set the domino it belongs to.

• Magnets. The first tap makes the domino a magnet with its + on the cell you tapped. A second tap turns it round, a third makes it neutral, a fourth clears it.
• Blanks. You only have to place the magnets: a domino you leave empty counts as neutral. Marking a domino neutral is a note for yourself.
• Notes. Press and hold a domino, or switch on Notes and tap, to note what it is not: not neutral (a small ± on each end), then not with its + on that cell, then not with its − there (the ruled out signs drawn faint and struck through). A tap skips whatever a note rules out.
• Numbers. A number turns grey when its line holds exactly that many of its pole, and red when the line holds more or can no longer reach it. Equal poles that touch glow red.
• Undo. Undo takes back your last change.
• Score. Your score is the time to finish the board, plus 30 seconds for every hint. Every board size has its own leaderboard.

Strategy tips

1. Start with zeros and full lines. A 0 among the + numbers keeps every + out of its line. A line whose + and − together fill every cell has no blanks at all, so every domino crossing it is a magnet.
2. Count the blanks. A row of 8 that needs 3 + and 2 − holds exactly 3 blank cells. Counting blanks is often what settles the neutral dominoes.
3. A magnet lying along a line gives it one of each. A domino lying flat in a row puts either nothing or one + and one − into that row, so a row that needs no − leaves all its flat dominoes neutral.
4. Equal poles push apart. Once a cell is sure to be a +, none of the cells beside it can be one. Follow the chain: one settled magnet often decides its neighbours.
5. Read two lines together. On the large boards, a domino standing across two rows puts its + in one and its − in the other. Weighing both rows at once settles dominoes that neither row settles alone.

FAQ

Is Magnets free to play?

Yes. Like every game on Play, it runs free in your browser, with no download and no account needed.

Do I have to mark the neutral dominoes?

No. The board is finished as soon as every number is met with no equal poles touching; dominoes left empty count as neutral.

What does a hint do?

It first puts right a domino you set wrong, or one whose note rules out its real setting. Otherwise it sets the next domino that logic forces from the board as it stands, outlines the rows, columns or cell that step reads, and the line under the board says which rule it used. Each hint adds 30 seconds to your time.

What are today's magnets?

Every day everyone plays the same medium 8 by 8 board, so times compare directly on the leaderboard.

How is my score counted?

Your score is the time from the first look at the board to the last magnet, plus 30 seconds for every hint. Lower is better.