Mosaic

Mosaic is a logic puzzle where numbers tell you how many cells in each 3×3 neighborhood should be filled—and your task is to use numbered clues to determine which cells to fill so that each 3×3 neighborhood matches its count.

Played on a square grid, it challenges you to determine which cells should be filled (typically shown in black) and which should remain empty (white), based on numerical clues placed in every cell.

Each number in the grid indicates how many cells in the 3×3 block centered on that cell—including the cell itself—should be filled. For example, a “0” means all nine cells in its neighborhood must be empty, while a “9” means they must all be filled. Edge and corner cells use smaller neighborhoods (e.g., a corner cell considers only a 2×2 area).

The puzzle is solved when every cell's clue is satisfied simultaneously. Despite its simple rule set, Mosaic offers rich logical depth: deductions often involve overlapping neighborhoods, counting constraints, and careful propagation of implications across the grid. Every puzzle is guaranteed to have a unique solution that can be reached through pure logic—no guessing required.

Color every square either black or white. Each number indicates how many black squares are in the 3×3 block centered on that number—including the numbered square itself.

Left-click an empty square to turn it black; right-click to turn it white. Click again on a filled square to cycle it through black, white, and empty. You can also left- or right-drag to set multiple squares at once.