I really enjoyed it, a horror game themed after ballet is pretty rare, as far as I'm aware! It's very original. And Tchaikovsky is always a pleasure to listen to!
If you were to make a longer version, it'd be really cool to get little hints about what happened to the kid, why she's haunting miss Pirouette, etc... just little details that would make the horror that much poignant.
It was really fun.