Convert green squares to either black or white according to the conditions of the game.
Primarily, a number square represents the number of black squares in a 3x3 group of 9 squares where it is the center square. Exceptions occur at the 4 corners and sides of the puzzle where a number square so located represents the number of black squares in surrounding subsets of 4 and 6 respectively.
Touch or left click to toggle a square between black, white and green. With a mouse, you can click and drag to affect multiple squares.