This game includes both a Challenge Mode and a Campaign Mode.
In Challenge Mode you have to complete a number of set goals.
There are 30 stages in total. You will be able to learn the basics here as well.
In Campaign Mode, all enemies will make an appearance.
You should not challenge this mode until after you've become fairly proficient at the game.
As soon as you start a stage, plants and animals will start appearing of their own accord.
The only thing the player can do is click plants to make them wither and click animals to kill them (this is called "culling").
Some animals and plants turn into nutrients when you cull them. Combine them to create stronger plants and animals!