The music and SFX are great, really ties the whole game together! Puzzles are a lot more complex than I thought they would be, there's some really interesting ideas here that I'd love to see explored in a full game. Art could use a revamp though, the simple character designs are butting up against the more detailed background and the colors could use some adjustment to make them more complementary (try using Adobe Color, it'll save you a ton of time picking colors).
EDIT: Just noticed the color assist mode, great idea!