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A Nikoli logic puzzle built entirely on sight lines. Every number counts the white cells it can see — itself plus everything up, down, left and right until a black cell or the wall cuts the view off. Paint cells black until every number is exactly right, keeping black cells apart and the white ones joined in one piece. Each 7×7 board has exactly one solution.
Each number stands on a white cell and tells you how many white cells that cell can see in total. Counting starts at the number itself, then runs outwards in all four directions, and each direction stops as soon as it meets a black cell or the edge of the grid. So a 7 means: myself, plus six more white cells spread across up, down, left and right.
Your job is to paint the right cells black. Numbered cells are always white and can never be painted. Two extra rules keep every board honest: no two black cells may sit side by side (diagonal contact is fine), and all the white cells must remain connected as a single group, so you can never wall a white area off from the rest.
Tap a cell to paint it black. Tap it again to leave a small dot, which marks a cell you have deduced must stay white — it costs nothing and stops you second-guessing the same square twice. A third tap clears it.
A number turns green the moment its sight line is exactly right, and red if you have blocked so much that it can no longer reach its total. Black cells that end up touching are shaded in red too. Every board has exactly one solution, reached by logic alone, and your finishing time is your score.
Start with the biggest and smallest numbers, because they are the least free. A 2 can see only one cell besides itself, which means three of its four neighbours are black — that is three certainties from a single clue. At the other end, a number as large as the grid is wide has to see all the way to at least one wall, so the whole of that line is forced white.
Remember that a number counts across two axes at once, and that is where the real deductions hide. If a clue already sees enough cells along its row, every extra cell it can reach along its column has to be cut off by a black cell, and vice versa. Work out the minimum each direction must contribute before you commit to anything.
Use the white dots as much as the black cells. The moment a number goes green, every further cell along its four sight lines is settled — the ones it counts are white, and the first cell beyond each stopping point is black. Marking those whites explicitly stops you from painting a cell that would quietly break a number you already finished.
Keep an eye on the connection rule while you paint, not afterwards. Black cells that trap a pocket of white against a wall or in a corner are a very common way to reach a board that satisfies every number and is still wrong. Any time you paint near an edge, ask how the white cells behind that paint will still reach the rest of the grid.