- For the level before the v1.8 update, see Sky City - Day 6 (Pre-1.8).
The point of this Brain Buster is relatively simple. Use sun to defeat zombies, and defeated zombies grant more sun (and points). Once you run out of sun, you lose. The target goal is 10000 points, which should not take very long. The player has two attacking methods, a cannon shot and a laser beam. Use these two attacking methods strategically. Some zombies have different movements as others. For instance, Zombie Fighters move fast and quickly, while Lightning Gun Zombies move diagonally. Double-Cabin Aircraft Zombies, when defeated, will cause a lightning storm. When this happens, quickly use any weapon as fast as you can, as no sun is spent during this state. There are no waves, so the player can go as fast or slow as they want to.
Hard Mode adds in new zombies and a new attacking method, which is a missile barrage. This will defeat many ordinary zombies in one shot, so use this when there are many zombies on screen in a group. 25000 points are needed to win this time, which can take at least 5 minutes. Double-Cabin Aircraft Zombies now do not cause a lightning storm, so the player cannot rely on them. Flying Gargantuars will scare off all zombies on screen in an event. This happens numerous times, and the player is not forced to defeat it. Do not attempt to defeat this if you don't have at least 4000 sun, as this has a lot of health, and attempting to defeat it can result in a loss if you do not have enough sun. However, once you reach about 4000 sun, you can defeat it with around 12 missile barrages. In return, the player gets a huge amount of points, as well as 2000 sun, almost refunding what it took to defeat it. Taking your time is key in this level.