Sudoku is played on a 9x9 grid. Rules:
1.Each row must contain the numbers 1-9 exactly once each.
2.Each column must contain the numbers 1-9 exactly once each.
3.Each 3*3 sub grid must contain the numbers 1-9 exactly once each.
How to play: Click a number to choose it, then click blank cells to fill it. Click again to remove it.
The color of the number you filled is green (or yellow in night mode). While the number is finished, its color becomes orange.