Neat idea. I don't think I would have ever thought of a reverse tetris concept, so that scores high on my creativity scale!
My two (minor) wishes:
1. Since I was playing on a touchscreen laptop, I kept trying to touch the piece to select it. Touching didn't work, I had to select with my laptop's touch pad. I wish I could have touched it using my touchscreen
2. I wish I could hold the arrow keys to move the pieces rather than needing to constantly tap the keys. Granted, press and hold would surely need some fine tuning to get right, but I think it might make for a nicer user experience
Wishes aside, I enjoyed playing. Great Job!