Very fun idea and I did enjoy playing.
I found it quite hard to actually get two opponents to hit each other so I ended up running around aimlessly and hoping for the best.
I think if you added a sprint, cover, explosive barrels and had enemies able to fire at angles the player would have more control about which enemy to kill off. But just a suggestion.
The art work is nice and I liked the increase in difficulty.
I would recommend.
Please play rate and give feedback on mine at https://itch.io/jam/gmtk-2018/rate/300505