It's a great idea, but it just needs a few more things in a second (which i hope you will make). Needs an incentive to kill people and some sort of treasure or items. 4/5 but with improvement it could definitely make 5/5.
the last feature is a bit dissapointing since you never run out of ammo if you can get gold on every level anyway. otherwise 5/5 looking forward to multiplayer.
the ending makes no sense and i have no idea why there are roadblocks in the sky. Also the difficulty is so easy until the spacey bit then it is so hard. 4/5 except for the ending and difficulty
 "Great Dungeon in the Sky"){kind=icon}
 "Gravitee Wars"){kind=icon}
 "Lucky Tower"){kind=icon}
 "Apokalyx"){kind=icon}
 "Ether Space Defense"){kind=icon}
 "The Great War of Prefectures"){kind=icon}
 "Epic Combo!"){kind=icon}
 "The Trader of Stories"){kind=icon}
 "Reachin' Pichin"){kind=icon}
 "Bunny Flags"){kind=icon}
 "Journalizm (unlocked)"){kind=icon}
 "Monster Slayers"){kind=icon}
 "Creative Kill Chamber"){kind=icon}