Things are missing.
Good game but some points to improve on. #1: The need to rebuild your health and defenses. #2: Maybe the game should pause when you are upgrading or buying weapons. I died because I could not decide on what to upgrade fast enough. I like that you run out of bullets but give me a melee weapon at least. #3: Random survivors could help since if we spend survivors at the wrong place in the wrong order, you lose. Otherwise not bad.