Cool game, well done for deciding to make the game in 3d, as far as I know, it's more difficult than in 2d. I think if you refine the game, then refine the artificial intelligence of the enemies, I often had them standing in one place and I just shot them. I would also add some bonuses to the game, well and maybe changed the logic of shooting, personally I was not comfortable to turn around to shoot.
In general, the game has prospects, and options where to develop the game is, good luck!!!)))))