1980s/90s coop shooter game help

Hi everyone,

I'm looking for a coop shooter game available on Amiga or Commodore 64 I think. It wan one of a group of games we got along with the computer when it was bought second hand.

From what I remember it had:

Characters holding a tube-like gun that cannot be pointed up/down. It fired large projectiles.

You started in a bunker that will explode as the game start.

It is room based not just side scrolling so you are able to go back to previous rooms. This meant you could move in 4 directions in the room but it wasn't a pure top-down perspective.

TIA