- For the level before the v1.8 update, see Sky City - Day 21 (Pre-1.8).
In normal mode, the player must defeat level 1 zombies.
This level is extremely difficult, especially since this level will start off with Coneheads and Bucketheads, Double-Cabin Aircraft Zombies will almost always kill one of your aerial plants, and Imps from the Transport Boat can severely weaken the defense on your ship if not payed attention. Strong cheap plants such as Magnifying Grass, as well as Cycloque should be used. The pre-selected Pea-nut is unviable in this level, considering the fact that most straight-shooters aren't very good in Sky City.
- The small number next to the zombie icon means that zombie will always appear in that lane, with 1 being the topmost lane and 5 being the bottommost one.
|Waves||Non-dynamic zombies||Ambush zombies||Note(s)|
|2||None||Carries 1x Plant Food.|
|3||None||Carries 1x Plant Food.|
|9||None||Carries 1x Plant Food.|
|10||None||Second flag (in-game).|
|11||2 4||None||Final wave.|
- Start off by planting Sun-shrooms.
- When the first Conehead appears, try setting up a defense while the ship's cannon takes care of it.
- Later into the game, Cycloque should be used to deal massive damage to flying zombies.
In hard mode, the player must defeat level 3-4 zombies.
This level is extremely difficult with level 3-4 zombies. With extra health and increased dps per bite damage, your plants should be upgraded to levels 3-4.
- Just like in normal mode, just repeat the same strategies but with upgraded plants.