Similar to minesweeper, each grid # indicates how many immediate squares should be filled in. "Immediate" includes the # square and all 8 surrounding squares. For example:
9: all 9 immediate squares are filled (6 for edges, 4 for corners)
0: all 9 immediate squares are empty
general: after filling x immediate squares, the other 9–x are empty (6–x for edges, 4–x for corners)
Only click on squares that should be filled in—a wrong click ends the game.
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