That was a pretty good start!
I was kind of expecting more story, but the fantastic art and great music was a pretty compelling hook that drew me in.
I liked switching gravity though those puzzles break my brain a little. Anyone else remember VVVVVV? The ghost attack is neat, too. Not a lot to say about the level design; it was starting to get interesting but then it ended. It's a demo, so that makes sense.
I found the control scheme kind of awkward, though. I didn't like having to take my fingers off the movement keys to perform actions; a two-handed scheme with z/x/c and the arrow keys would have been better, or even just moving the actions to ctrl/alt/shift.
I definitely ran into glitches as well. I managed to get a box stuck in terrain, and then it fell off the map on the last level. Good thing it has level restart! Also, the text box when talking to the NPC that gives you the powerup is super blurry for me.
Any plans to continue this or is your focus elsewhere now?