I am incredibly impressed with how polished this game looks and feels. The tutorial/main menu area has a production level presentation.
Things I think your game excels at:
- Presentation (seriously)
- Game feel
- Level design
- Sound design
The gameplay loop for me reminded me of playing COD Zombies, as I was constantly leading the enemies away from the boxes so I'd have time to push them. I had a lot of fun trying to find new paths to take to more effectively train the enemies and that added an extra depth that really brings the game to a whole new level.
The only other feedback I can think of is that on level one I feel like there were too many enemies. It certainly wasn't too hard, but given that your game has multiple levels it felt like it was stepping just a little too into the deep end too early, which also might not necessarily be a bad thing since that's what gave it that COD Zombies feel that I experience. I also played using the revolver which could have been a bad choice on my part.
Seriously good job. This is one of those games that gives me the "wow I wish I made this" feel.