Great game!
You're a genius man! Incredible idea, to mix tetris and plataform...just a sugestion, it could have "themes", like medieval or something as you're progressing in the game. And so the tetris song could have more variety of styles.
And about the "restart button", they're right, you could make it visible, because some people don't know that most plataform games you just have to press "R" like you did.