I enjoyed your game, I especially like the design of it. It felt difficult at first with not knowing where the enemies were and learning the gun mechanics. For the nail gun, I would make the projectile slightly bigger that way I can easily see where my bullets are going since there is no reticle. I would also make the nail gun a pickup item midway through the level since the starting area is open because it felt kind of easy dealing with the starting enemies with the nail gun. I also noticed that the enemy would sometimes get stuck on obstacles when chasing me. if you decide to further develop the game it would be cool to see more levels and different enemy types. Overall you guy did a great job designing and executing this game.