Love the setting / design- the underground russian train system idea is wacky, but definitely appropriate. Love it!
Gameply was super easy to 'pick up and go', and I'm really glad you made it super simply to just hop back in and keep playing after each death.
Difficulty curve is perfect, and I love that it doesn't just "start over at the beginning", but rather continues in the tunnel from exactly where you died.
Overall great work, the only thing bringing a star down is the lack of SFX. I would have liked something like a motor "put-put", train "whoosh"-ing by, and a collision... I would say if you had these then music would not even be necessary.