Doomsday Tower Defense: Awakening at the Beginning and Infinite Growth Tower

One day, the sky around the world split open. A scarlet countdown appears over all cities. [The era of global tower defense begins] [Each person is bound to a natal defense tower] [At midnight every night, the zombie tide refreshes] [Those who lose the defense zone will be erased] [If you defend for seven consecutive nights, you can activate the regional joint defense line] Since then, human society has been forced to rewrite.