Got kinda absorbed by the game, spent almost 2h and got 16060 point. I stopped because I have to sleep. ^^
I've never ran out of Passes, so I don't know if the Three Passes thing is in yet, but if it is, maybe hard cap to only three (with refill every 5 line until cap is reached again)
A discrete background would also be a nice addition, rahter than solid dark blue.
Audio and visual when clearing lines were really satisfying. So was the sound taht plays when you can't place a tile.
But maybe add more audio cues when clearing lines? I counted 3 different ones, but you can make up to 5 lines/columns simultaneously, so one for for each number could be the best :D
And a nice background music :)
Regarding graphics, the only thing that slighty bother me is the fact that I can't tell right away if the block I controll is collinding with the other blocks. If you could hilght the blocks on the grid that are colliding with one I'm trying to place, it would be better. It's the only key thing that's missing I think.
Overall, clearly a nice spin on a classic game, very well executed, but could use a little bit of audio/graphical polish.
Cheers!