Interesting idea, but frustrating.
I think I see what you're trying to do here, but it's pretty frustrating to play at first. I eventually figured out to set the pieces so that they move into each other as part of their patterns.... but for awhile I couldn't figure out if my mouse or your game was broken. More explanation at the start of the game would be nice.
The graphics do the job, though more variety in pieces and backdrops would be good.
While I like this music, it's also used in another popular game (Sushi Cat, I think?), so you might consider using something else.