Man, this is the best Tetris on the Game Boy easily, and really the best feeling retro Tetris so far. Cutting out the 8th pixel per tile so that the well is 20 blocks high despite the GB/GBC screen resolution is genius. The music and SFX are so fun. And slamming a tetrimino down on the Krakens tentacle and watching him get all pissy is such a great touch.
I just tried out the new ghost piece hack and it's even better. Well done, Matt! I'll be enjoying this one for many hours to come.