In normal mode, the player has to beat the zombies at level 1.
Difficulty
This level properly introduces the Lightning Gun Zombie, the zombie embodiment of a thunderbolt. Anthurium is pre-selected in this level, meaning that it must be used against Lightning Gun Zombies. Other than that, the player should also worry about Zombie Fighter.
Strategies
Plant Anthuriums on column 2. This is so that your sun producers, as well as some plants on the ship won't get status effects.
Shoveling plants on the sky who are affected by the thunderstorm or by Lightning Gun Zombie is unwise, as they can be used as meatshields to block the Zombie Fighter's bullets.
Loquats should be used to do heavy damage to zombies.
In hard mode, the player has to defeat leveled-up zombies.
Difficulty
With upgraded zombies, that means the player should upgrade their plants, especially Anthurium, at max level. The player should also bring upgraded Pineapples to counter the Zombie Fighter.
Strategies
Do as what you did in normal mode, but with leveled-up plants.
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 lane.
