Mosaic

Decide every square: it either holds a purple square or is clear. Each number indicates how many purple squares are in the 3×3 square surrounding the number – including the clue square itself.

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 square to turn it purple, then clear, then empty again. Right-click it to turn it clear, then purple, then empty again. Keep the button down and drag to do the same to every square 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 square under it, and Space what a right-click does.

The drag works for clearing too: start on a shaded square and the shaded squares you pass over are cleared with it. A whole drag is one step of Undo.

What the squares show

A square you have made clear turns yellow, which tells it from a square you have not decided yet. It carries a faint cross too, unless it has a number, which then has the square to itself. A number is drawn on top of whatever its square holds, and fades once its 3×3 square is fully decided and agrees with it.

Hints

Hint explains the next step rather than simply making it. It reasons only from the numbers and the squares you have already made purple or clear, so it carries on from wherever you are, as long as none of them is wrong; if one is, it asks you to fix the highlighted mistakes first. A number’s squares, in its words, are its block: the number’s own square and the eight around it, fewer at the edge of the grid.

• A ring marks the squares the step decides; the sentence says whether they must be purple or clear.
• An outline marks the block of each number the step reasons from: the number’s own square and the eight around it. The number itself is circled.

Most steps come from one number alone:

• A number that has all its purple squares makes the rest of its block clear.
• A number with only as many squares left that are not clear as it needs makes all of those purple.

Where no number settles a square alone, the hint compares two numbers whose blocks overlap. Both count the squares the blocks share, so the two differ only by the squares one of them counts and the other does not:

• A number that needs more purple squares than another, by as many as it has empty squares outside the other’s block, makes all of those purple. A 6 beside a 3, with three of its empty squares outside the 3’s block, is the plainest case.
• Two numbers that need the same number of purple squares, where every empty square of the first is in the second’s block too, make the second’s other squares clear: the second gets all it needs from the squares they share.

Where the two are the same number, the hint names each by where it sits: the upper 7 and the lower 7, or the left 7 and the right 7.

An Easy puzzle as the game deals it is finished one number at a time, and never needs a comparison. A Normal one needs comparisons, and they finish it. On an Unreasonable board there comes a point where comparing numbers settles no square either, and the hint says that nothing further follows by deduction instead of choosing for you. Save your position and try a square beside a number with few squares left. The hint carries on from whatever you mark.

Mosaic parameters

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

Width, Height

Size of the grid in squares. The grid may hold at most 10000 squares. A long thin puzzle is rare, so on a grid fewer than 20 squares across a long one can take a minute or two to appear, or none is found. Each must be at least 3.

Difficulty

Determine the difficulty of the generated puzzle; see what the names mean. An Easy puzzle can be finished one number at a time: there is always a number that already has its shaded squares, or that needs every square it has left. A Normal one stops giving such a number somewhere, and there you compare two numbers whose blocks overlap. An Unreasonable one has a single solution that neither of those will reach, so somewhere you have to try a square and see what follows. The Hint button stops where the comparing does.

Aggressive generation

Every puzzle hides the clues the game never used while solving it. When on, the game also tries taking away each clue that remains, and keeps it away whenever the puzzle still has its one solution at its difficulty without it, so fewer numbers are shown, which usually makes the puzzle harder. Above Easy it makes a large puzzle much slower to find.

More help

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