This is fun and works good! I like how your goal is simple and notable straight from the beginning.
I was hoping there would be more feedback from the bullet hit. I were missing some boxes laying on the ground to hide from the lasers and the bullets. Also missing the gun-wielded robots to shoot visible bullets while the other characters shoots visible projectiles as well. While the characters pistol wont go trough the enemies, it would be do harm to the robots as well.