This is quite neat. The simple graphics are pleasing, as is the musix/sfx. Puzzes build gradually on top of each other gradually getting trickier.
I must admit that my playthrough almost came to an end in an early section of the game
since ı managed to lock myself in one of the first puzzles.
Perhaps the above state is solvable, but I could not figure it out. I worked around it by replaying the first section and then got through the puzzle on the first try.
Any way. The only thing I'm really missing here is a save feature, and possible also a puzzle select screen. To make a long story short: Nice work!