I enjoyed this! The music was chill, the color palette is easy on the eyes, and the variety of backgrounds was cool. I appreciated seeing some pieces from Tetris 2/Tetris Flash and Gussun Oyoyo in a new context. The balance of the game seems carefully considered and I appreciate that, even though I sometimes grit my teeth and scream out for an I piece that appears to be outside of the piece set.
Given how involved the game can be, it's kind of easy to forget about or even ignore the timer; I would've appreciated some juice to motivate the player to play faster when the clock is nearly running out: maybe even giving them more time for making impressive clears, like doubles?