Good effort
I made a couple of fps shooters when i started out too, and i know there no easy task, but a few tips, limited ammo means limited fun! Simple characters that move well will score higher than advanced characters that don't... seperate the peices and have them spin to look at you when they emerge. Furthermore add a health bar and a damage code on the peak of the enemies apearance / momement, so you have to kill them or they'll shoot you! I liked your preloader... the sound was a bit annoying though! Good job! Keep it up!