Filling

Write a number in every blank square of the grid. When the grid is full, every orthogonally connected group of identical numbers should have an area equal to that number: so 1s always appear alone, 2s in pairs, and so on.

Controls

On a touch screen, a tap does what a click does. A key the puzzle’s controls show as a button can be pressed there instead of on a keyboard.

To place a number, click the mouse in a blank square to select it, then type the number you want on the keyboard. You can also drag to select multiple squares, and then type a number to place it in all of them. To erase numbers, select one or more squares in the same way and then press Backspace.

To play with a keyboard, use the arrow keys to move the cursor and type a number to write it in the square under the cursor. Press Space to add the square under the cursor to a selection (or take it out again), or press Enter and then move the cursor to select every square it passes over; typing a number then fills the whole selection. Escape clears the selection.

Hints

Hint explains the next step rather than simply making it. It reasons from the numbers given and the numbers you have written, 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 ring marks each square the step fills. The number to write there is the one the sentence names.
• An outline marks the neighbors the reason rests on, when it is about the number a square can take rather than about one region.
• Stripes mark the region the sentence names: a group of equal numbers already on the board that is not yet as big as its number. The squares the step fills take that same number.

A few ideas are worth learning by name:

• A region that must grow. When a region of 6 has fewer than six squares and only one empty square beside it, or every way it could reach six passes through the same squares, those squares must be 6 too.
• An exact fit. When the empty space a region can reach holds exactly as many squares as it is missing, it fills them all.
• A lonely square. A square that no neighboring region can grow to include can only be a 1.
• Nothing else fits. When every other number in a square would break the rule, by touching an equal number or by leaving some region short of its size, the one that is left must go there.

On an Unreasonable board there comes a point where none of these settles another square, and the hint says that nothing further follows by deduction instead of choosing for you. On a small board that can be the very first thing it says. Save your position and try a number in a square that has few it could take, beside a region that still has to grow: if it is wrong, a region nearby is soon too big or shut in too small. The hint carries on from whatever you enter.

Filling parameters

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

Width, Height

Size of the grid in squares. Filling a board with regions that obey the rule succeeds less often as the grid grows, so a board much past 300 squares can take a minute or two to appear, or none is found. Each must be at least 1.

Difficulty

Determine the difficulty of the generated puzzle; see what the names mean. An Easy puzzle can be finished one forced square at a time: some region can only grow one way, or some square has one number left. An Unreasonable one has a single solution that those steps stop short of, so somewhere you have to try a number in a square and see what follows. The Hint button stops where the forced squares do.

More help

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