Nice work, interesting concept.
Maybe it's a little boring to play sometimes. I think the difficulty could increase faster at least in the hard mode.
It seems that the mechanics of rotating the pieces are absent on the easy and medium levels. So the game becomes just a matter of frantically pressing the space bar until a piece fits. It's a bit of a shame. Maybe you could rather change the number of different pieces to vary the difficulty.
Also I would have appreciated a clearer score. The score you are proposing is more like statistics. Its cool to have them but I also would like to have an unique number that is also displayed while I'm playing to motivate me to surpass myself.
Nice work on the one button menu !