Range

Shade some squares, so as to meet the following conditions. A shaded square holds a purple square; every other square is clear.

• No two shaded squares are orthogonally adjacent.
• No group of clear squares is separated from the rest of the grid by shaded squares.
• Each numbered cell can see precisely that many clear squares in total by looking in all four orthogonal directions, counting itself. Shaded squares block the view.

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 color it purple. Right-click it to mark it with a cross, if you know it should not be purple. 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.

A cross is your own note that a square is clear. Clicking again moves on round the same three states: a left-click turns a purple square into a cross and a cross back into an empty square, and a right-click turns a cross purple and a purple square empty.

Hold Shift while moving the cursor to put a cross in every empty square it passes over.

What a number sees

Since shaded squares block the view, a 2 clue, for example, must be adjacent to three shaded squares or grid edges, and in the fourth direction there must be one clear square and then a shaded one beyond it.

The numbered cells sit on a lighter square. They are always clear, and cannot be changed.

Hints

Hint explains the next step rather than simply making it. It reasons only from the numbers, your purple squares and your crosses, 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. Its sentences call a square a cell, and when one says a cell “must be clear” it means you can mark it with a cross.

• A ring marks the cell the step decides.
• An outline marks what the step reasons from: the cells a clue already sees, the cells around one that purple would cut off, or a purple square beside it, which takes a doubled outline. The clue the step counts from has its number drawn in the hint color.
• Stripes mark the run a clue has to see along, from the clue as far as the ringed cell.

The ideas it teaches:

• Shaded squares never touch, so every cell beside a purple square is clear.
• A clue that sees enough stops at the first cell past what it sees, so that cell must be purple. Likewise, a cell that would let a clue see too far must be purple.
• A clue that needs to see further than its other directions allow must see along the rest of the way, so those cells are clear.
• Clear stays connected. A cell that would cut some of the clear cells around it off from the rest, if it were shaded, must stay clear.

On an Unreasonable board there comes a point where none of these settles a cell. The hint then says that nothing further follows by deduction instead of choosing for you. Save your position and try a cell beside a number that is close to its count, purple or with a cross: if it is wrong, a few forced cells later some number can no longer see enough, or sees too much, and shows in red. The hint carries on from whatever you decide.

Range 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, and together they can come to at most 128. 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: there is always a number whose view settles a square, a purple square with an undecided neighbor, or a square that would cut the clear squares in two. An Unreasonable one has a single solution that those steps stop short of, so somewhere you have to try 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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