That took some getting used to before I could kill the opponent. All the special effects when I fire made it difficult to see much at all, and very difficult to see where the enemy was going and whether or not I was hitting him. That makes it tough, and I suspect most players would want to be able to see what they're doing better and have the challenge come from the opponent being powerful instead of having their own shots obscure their view.
When I was playing, most of the battle took place outside of the buildings area and in an open field. So it ended up being just a matter of holding left or right to strafe around and avoid being hit, while I tried to keep the enemy in the crosshairs and fire short bursts so my shots didn't obscure my view. Then I tried playing again and staying within the buildings area to see if that made it more fun, but it started to seem unfair that the enemy could sneak up and tag me while I was having trouble finding him at all among the buildings, and it got practically impossible to follow the enemy when he started jumping around. Then I got hit and thrown in the air and landed on a rooftop with a small fence-like thing at the ledge with no way of getting off.
This is a very nice engine (idk how much of the engine you made yourself or how much came with the programming package you were using), but there's still a lot of work ahead to turn it into a really fun game.