Nice solo effort, I'm not sure how the project file size is 1.2GB though, for a demo like this it should be a couple of hundred megs. It may be the asset pack you used, I would have preferred static targets to ones that are running into the walls. The enemy model aesthetic was too realistic for the scene design. With the walls it looks like the texture tile map was being stretched. You could have just gone for a plain low poly look, single or a few colours from a set colour palate and matched the theme, that would have felt better for me. The shooting felt good and the sound effects too, the explosions looked good but again were too real, I would have preferred something more matching the whole scene.