level 15 was particularly difficult
liked the levels and difficulty very much
as other comments said graphics could be easily improved (although i am myself a very bad artist and understand your pain)
i don't really care about music so no big deal for me
overall good but... the fact that it looks like it has been made with paint is... not good

This is a solid though fairly basic puzzle game. Although the presentation is fairly bland, the puzzle design is consistently good and straightforward. The one weird thing I noticed is that -- to me anyway -- Puzzle 15 seemed to be the trickiest, with the ones to come after it all being easier (and I don't think this was the result of me getting better at the puzzles, either).

Other than improvements to the presentation (music/sound -- with a mute option, of course -- and graphics or even just a story or theme would help), the best addition I can think to add to the game is to actually save the minimum number of moves the player uses to solve each puzzle and tell what the minimum possible is, to possibly give some replay value to some of the puzzles.

Very good game idea, really innovative. It just looks bad. Try to make contrasts with those colors instead of just randomly picking them. Fading and scrolling effects would also be nice to have.

Fun and challenging gameplay. I like the option to undo moves that have been made instead of restarting the whole level. The lack of music or any sound makes it a somewhat dull experience though.