Lovely visual design. Pleasant color palette and smooth animation (with some great negative motion--love the skirt and hair). Jaunty music. Nice, sharp controls, a must for a twitchy platformer.
I must admit that found the game quite difficult. This is basically Ninja Gaiden, but with algebra thrown in. :) I made it to the Observatory, but after that, the constellations beat me up over and over again.
As a minor point, I must say that I didn't get much of a "horror" feel. I can imagine that getting stuck at work overnight with enchanted books and furniture would be threatening in real life, but the audiovisual design is cute, rather than threatening.