Nice take on a classic
I remember Tetris for the old school Game Boy. This really brings back memories. It's solid and easy to play, plus I really liked the background. The option to turn off the music was nice too.
Speaking of music, one of my favorite things about Tetris was the music (That annoyed me about the DS version. The original music wasn't even an option!). I really dug the remix you used. Is there an MP3 of that floating around?
Anyway, Cool game you got here! I voted to protect it.
That being said, there are two things I wanted to mention in the way of improvement. One of them is really minor and the other might be a figment of my imagination.
First off, there's no preloader. This isn't a big deal or anything, but I know folks who take off points for that sort of thing.
Second, I started to see patterns in what blocks were dropping. I'd get a whole lot of one kind five or six times in a row, or it would alternate between two blocks for a while. It might have just been a weird coincidence, but I thought I'd mention it.