http://livejournal.com/~phree_radical/
I've been working on the engine for the past three weeks or so and I believe it is now 100% accurate (I hope someone who's given their soul up to Tetris Attack at some point is around to appreciate this)!
There's a most excellent video of it in action (before I started animating the Yoshi stage) in the most recent post
And here is screenshot (takes one now)
So step one is to finish making it a perfect clone of Tetris Attack, and then I'll work on the new modes, hidden features etc.