Great game. Took me a while to figure out that only the dark colored parts of the blocks were what would be solid, and took me a while to figure out how to beat the levels.
One suggestion would be to have an instant drop and a slow drop like how most tetris games do. Sometimes i would want to drop the block to a certain point so i can slot it in somewhere, but the S key pretty much always brings it straight down to the floor wherever it is. Great submission!