Walking Zombies-Plants Guard War

A war story between plants and zombies.
It can be synthesized and upgraded, and cooperated to fight against the invasion of zombies. In this war, the trick is to win the war
The most critical place. That is to constantly upgrade your plants to make it have a higher attack power.
The secret of zombies: After being defeated, zombies will drop some useful things, collect them as much as possible. Big zombies need more plants to work together to be defeated.
How to play: Two plants of the same level and type can be synthesized with each other, and a stronger plant can be obtained after synthesis.
Game trick: Keep moving plants in the right place and clean up all the zombies.