Put digits in the empty squares such that in each row and in each column the digits 1-9 appear exactly once,
and they appear exactly once in the 3 × 3 "blocks".
Turn on "Error Checking" in the Settings menu for some extra help (duplicate digits then turn red).
Solve all three puzzles of one day (Light, Medium, and Heavy) and get a star! For each three Light puzzles you solve in one day you get a feather, for each three Medium a medal, and for each three Heavy an anvil!
Watch videos for extra puzzles.
Please send your feedback / bug reports etc. to firstname.lastname@example.org