I love the style you've gone for, and the decision to go for a ghostly theme (both gives a good reason for the flight while portraying that idea of being an 'enemy'). Also the ghost is adorable.
Gameplay is simple, but very responsive and clean. Definitely ramps up in the third level, but still felt like every death was my own misjudgement.
I'd love to see the Tetris theme brought in more, perhaps have the blocks build up at the bottom of the screen and delete rows? Could add some growing tension as the screen fills.