Some incredible artwork, I loved the enemy designs and environments made of cardboard. It really gave your game some personality on top of well defined characters tied into a nice little story about global domination.
It does seem to be a standard shooter affair. I tried to see how the difference came through but I realised if you played one character who could switch weapons then the experience would largely have been the same, gameplay-wise. Perhaps there could be more emphasis on their differences for the player to have to make decisions on during battle, like certain enemies being susceptible to particular weapons or certain characters having unique traits such as speed or strength differences.
Overall, a very solid playthrough and top notch presentation. Great work!