Very cool, very hard. In fact I'm wondering if the shapes (when randomly chosen?) don't make it impossible for the player to keep the game going indefinitely (as you clearly can in Tetris). I wish I had the proof chops to examine this claim.
The worst state in Tetris is the endless stream of "zig zag" shapes, but at least with those you can alternately sacrifice and clear rows, usually.
With this, I am not convinced that the pieces are allocated in a way that remains playable. I have cleared a couple of rows (in different games!) but there just seems too much stacked against me for progress.
It could be due to my eyesight; the board area needs visual hints. It could also be due to the controls, which seem like deliberate hardship.
It is cool, but it's too difficult to be fun; there's almost no recovery possible from accidents and there are too many ways to have accidents.
(I only managed to clear one row.)