The mechanics are easy to understand, and clearly hard to really master. I love simple games like this that have a lot more depth than it first appears. I played this for much longer than I realized. Excellent work here.
I'd love to see how this game would play if you were able to pick up a block from underneath you. As it is, once you fill in a layer, you permanently have a smaller field to play in. Obviously you can combine blocks in to the "floor" now.
I might also be interesting to explore having multiple lives. Getting crushed takes a life and puts you back on top of the pile. A column filling up also takes a life and blows up part of that column. Those sorts of things. There's a ton of potential with this idea in its simplicity and ease of playing for a few minutes at a time.
Literally the only criticism I have here is that I wish there was some notion of lives or some mechanic where a single mistake doesn't end your run. My best score so far is 1100, but I'm going to keep playing. Excellent work.
Update: Broke into the 2k range with a score of 2100 :)
Update2: Hit 2640. I gotta stop playing and keep reviewing other games. I'll be back for more. Also -- I set up JoyToKey so I could play with a controller and it makes this game feel even better *chef's kiss*