We had an idea similar to this at first, inspired by the "No Internet Connection" dinosaur game. It's quite simple but it works well. I found the overall pace of the game to be quite slow, I think I prefer more nervous gameplay when I hear "Run and Gun", the main issue with this slow pace, is that interval between fire and bullet speed are so slow, that most of the time, it's more interesting to avoid everything instead of trying to kill the monsteres.
Thanks for your entry!