very fun
i loved it but it needs to be improved
i have some ideas on that.
1.defense mode
-you should get more experiance when you kill certain monsters
-base should have defenceive guns
2.survival mode
-same as above
-you should be able to save you're progress at any time you want as well with loading and the same thing for defence
-options and music
-cheats
i hope that should help you with making it better and it's still a kick ass game