Code review for first Piston try

Hello Community!

I have been directed here as I am gonna do my first steps into rust lang. I have created my implementation of tetris in rust using Piston game engine. I would very appreciate to get some nice hints so I can increase my rust skill. My repository is open and available here: _https://github.com/Wowo10/rust_piston_tetris_. I hope I do not violate forum rules anyhow.

Thanks in advance!
Wowo