The sound is stellar, and the art as well. I especially like the dynamics & use of colors, though the black outline on the key & lock can look a little harsh. The 3D aspect & empty void as background also take some getting used to.
The gameplay is quite interesting, and even though it never challenges you to explore the full potential of its turn-based nature (see Rust Bucket by Nitrome for inspiration) it keeps up the pacing & ends quickly to prevent it from getting dull (which is something that Rust Bucket fails). I would've liked to see it end on a higher note though, like a boss fight.
Anyways, I'm curious to what inspired you to make this. Just some random idea that you had to get out of your head & turn into a game?