Not too shabby.
I beat this on my first playthrough, but that's only thanks to a bug. As people have already mentioned, some enemies shoot through walls, bodies get in the way of bullets (even if you're aiming over them), and towards the end of the game I lagged a lot.
I probably would've died on the zombie boss had he not glitched out. Like, he was coming for me, then got stuck against a box so I just shot his head over the box. Once I got his gun it was pretty easy from there.
I did like the final battle, despite the fact that it was pretty laggy for me. Jesus and Clown at the same time :O... But yeah, decent game overall, but you should try and resubmit it without the bugs.