Did you play Disoku? Try to get in a square of 3, 4, 5 or 7 cells, on each row and column different numbers and colours.
At Disoku Pro you have real brainteasers for experts, with puzzles of size 5, 7 and 8. Most of the puzzles show a nice symmetric pattern. There are 120 puzzles with different sizes and difficulty. Some of them are just solvable within 25 minutes. If you are not an expert, you will be after solving these real mindbusters.