Missing stuff + Glitch(es).
First, it needs candidates. The little numbers that go into the squares that show what numbers can still be placed in a certain square. These are ESSENTIAL for high-level puzzles. -1.
Second. There wasn't a difficulty setting that I saw. I think I got a harder puzzle after finishing the first one, but that honestly could have been my imagination. If there are different levels, let US change them, too. -1.
Third. This is the deal-breaker glitch. I had just finished one puzzle, and had moved onto the second one. I finished the second one, but I didn't get the win screen... So I thought I had messed up. I clicked on 'Hint', and guess what...? Sigh. It put a 5 in a box that already had a set 5. The puzzle solution was wrong / broken. Upon further investigation, I got several boards that started with incorrect number sets.... http://s993.photobucket.com /albums/af56/OCGamerNG/Glitches/ I posted two there. -4.
Fourth... Get rid of the boxy-thing that pops up for number input. It blocks the view and is a general pain in the butt when trying to find numbers, particularly in the 3x3 boxes. Have a thing along the side of the puzzle or, better yet, let us use the keyboard for putting in numbers. Not enough of a nuisance to minus points for... but close.
Next... I really liked the colors you had on the numbers. That made it much easier to group numbers and quickly figure out which numbers were missing from a row / column / box. Might I suggest changing it to be green for 1, 4, and 7, blue for 2, 5, and 8, and red for 3, 6, and 9? I think it might be easier to use the colors if they go down the number pad rather than diagonally. +1 for innovation.
The music was.. okay. The monster set made it harder for me to play... Probably because I'm so used to numbers. No score change for those, as they're mostly personal opinion / preference.
So.... 10-1-1-4+1 = 5. Test thoroughly next time, please? I'm using Firefox if that makes a difference.