With dozens of distinct plants and specialized zombie types, no two levels play out exactly the same way.

If you can, buy the game. The creator, George Fan, designed a masterpiece that deserves support. But if you are on a Chromebook in a high school library with five minutes left in class, and the IT guy has blocked everything else... go ahead. Plant those sunflowers. Eat those brains. Just be sure to close the tab before the bell rings.