"Plants vs. Zombies 2" is a free-to-play tower defense game that pits plants against a horde of oncoming zombies. The player harvests sunlight to purchase plants that each come with a special ability, and the zombies evolve to match. Successfully protecting the house for the duration of the level allows the player to continue onwards. Coins can be used to purchase power-ups, while plant food augments plants with power boosts.
Unlike its predecessor, "Plants vs. Zombies 2" introduces a time travel conceit that allows it to set up various worlds that the player must travel through. Each world consists of 25 levels and revolves around stopping the evil Dr. Zomboss from creating an alternate universe where zombies are the primary species. With over 25 million downloads, "Plants vs. Zombies 2" has outperformed the original despite some mild controversy over its free-to-play model that alienated some fans. However, Mike Fahey of Kotaku gave the sequel a glowing review, praising the game for implementing a system that allowed him to progress for free if he desired. Current worlds are themed around ancient Egypt, piracy and the Old West. Players can unlock two more worlds via downloadable content: the future and the Dark Ages.