I'm a huge Tetris nerd, so I'm curious: is this going to be old-school Tetris (eg. like NES Tetris) or a more modern version (eg. like TetrisFriends)?

Also, I'd recommend you have a few different modes of Tetris. Sprint (clear 40 lines as fast as you can) and Ultra (get as many points in a certain time limit) would be a good start.