Great idea for a game!
The controls could use a bit of work, here are some suggestions:
- Moving rotate to A or B like in other tetris games, so that your left thumb isn't doing all the work
- Adding some sort of auto-shift/auto-repeat to left and right; the lack of this plus the fact that the pieces spawn on the left means that you have to press right a bunch of times to place something on the right edge of the board
Some sound effects would really help a ton too, but I'm sure you know this and time constraints were the issue.
The graphics were pretty fun too! Interested to see where this goes if you keep working on it.