I love this, a great take on Dr Mario but with some extra variables and more time to think. I like that they fall into gaps also rather than staying as sections like in Tetris.
Having made a Tetris mod before I wonder if you came up against the hurdle of trying to work out what were solid connected blocks and which were broken and should fall through gaps, which turns out to be quite difficult, better to go one way or the other. Tetris has none fall, you have all of them fall.