Kurodoko

How to Play Kurodoko

Kurodoko (also known as Kuromasu) is a Japanese logic puzzle played on a grid. Your goal is to shade some squares black so the remaining white squares obey the number clues and form a single connected region. Each clue is a promise about visibility: it tells you how many white squares can be seen from that cell in straight lines horizontally and vertically, counting the clue cell itself. Sightlines stop when they hit a black square or the edge of the board.

To solve the puzzle, you decide which empty squares become black. Black squares may never touch each other orthogonally (sharing an edge), although diagonal contact is allowed. All white squares must stay connected as one continuous group. These three ideas—visibility counts, no adjacent black cells, and connected white space—are the heart of every Kurodoko puzzle.

Use the tools above to mark cells. “Paint Black” toggles black cells, “Mark White” places a dot to indicate a confirmed white cell, and “Erase” removes your markings. On desktop, right-click or Shift+Click marks white quickly. On mobile, tap a tool first, then tap the board. The puzzle is solved the moment every number is satisfied, no black cells touch, and all white cells connect in a single region.

Strategy Tips

• Large numbers want long sightlines. Start with the biggest clues and make sure they have enough open space.
• If a clue already sees enough white cells, the next square in that direction must be black.
• Black cells cannot touch—if one cell is black, its four neighbors are automatically white.
• Keep the white area connected. Avoid placing blacks that would split the board into separate islands.
• Use dots to track confirmed white cells so you don’t over-shade later.
• When you’re stuck, scan for a clue that is almost satisfied in one direction.
• Check the edges: corner clues often lock in black cells quickly because sightlines are shorter.

Keyboard & Touch Controls

Move the selection with Arrow Keys or WASD. Press Space to toggle black, X to mark white, and Backspace to erase. Press R to restart and N for a new puzzle. On touch devices, use the tool buttons to choose what to place, then tap the grid.