Plants vs. Zombies takes place on a lawn broken into rows and columns. Just beyond the left edge of the screen is your house, while just beyond the right side of the screen is the street. At the top of the screen is a seed tray that displays your current amount of sun as well as whatever seed packets you have available.
During each level, zombies slowly make their way leftward from the street towards your home. Your job is to resist the zombie attack by collecting sun and using it to buy various defensive plants to place on your lawn. If you destroy all the zombies in a level, you proceed to the next level. If a zombie makes it all the way to the left side of the screen, you lose.