It was okay, but it took me literally 10 minutes to figure out how to play. You should make it more clear, perhaps with a hint like "HINT: The background can affect the foreground".
It was also very short, though that's understandable with it being experimental. You should make a full game (though again, make it more obvious as to what to do).
The graphics were good, and the sound was rather... classic, as if off of an old game. Individually they work fine, but they're not as good together. Perhaps make the visuals look less refined (as opposed to the music).
Unoriginal, but good.
i love games with original ideas like this
For the sequel you should make the levels bigger and more complex. It gets too easy once you figure out what to do. Otherwise I see a lot of potential with this.