A neat project to learn game dev, but there are far better free Tetris games out there.
You did a decent job on this, I didn't notice any bugs, but the controls feel kinda clunky. I don't see a reason to limit controls to arrow keys. Why not Z and X to rotate, allowing UP to quick-drop?
The pieces are a little sticky, would be nice if I could move horizontal even when the piece reaches the bottom. and i don't like that i can't move left or right once down is pressed.
Finally, the game feels pretty boring, no sounds or music, it takes a while for pieces to drop (especially since the down button is a big commitment) and no cool effects. you could probably earn 2 more stars from me just by adding some juice.