The idea here is fun, though I think it is missing a few crucial things that are holding it back.
There is no crosshair on-screen so it's hard to tell where my bullet will hit, and the robots have no reaction to getting shot except for when they die, so a lot of the time I didn't know if I was doing anything. I also found the mouse sensitivity to be extremely low where it felt like I couldn't even aim too.
Otherwise there is some groundwork for quite an interesting game here, I quite liked the apocalyptic soundscape and the world outside the train, very cool!