www.mathdoku.com
Many free puzzles playable online, in three sizes: 4x4, 6x6, and 8x8, in three difficulty levels. Also has "no-op" puzzles (where the operator clue is not given).
Many free puzzles playable online, in three sizes: 4x4, 6x6, and 8x8, in three difficulty levels. Also has "no-op" puzzles (where the operator clue is not given).