Took me a while to figure out that different colored blocks had different gravities. It's a good idea, I wish I had a friend with me to play it together.
I blocked myself by accident in a couple of levels by pushing the blocks next to a wall. I don't know if this situation is something the player needs to look out for or just an edge case you didn't get a chance to polish.
Would love to see more levels. Check out our game if you have the time :)