Fill the 9x9 grid so that every row, every column and every 3x3 box contains the numbers 1 to 9 exactly once. The bold numbers are given and cannot be changed.
Tap a square, then tap a number below (or type it). A wrong number turns red and counts as a mistake. Hint fills in a square for you but adds 20 seconds. Pick Easy, Medium or Hard, and your best time for each is saved.