Plants vs. Zombies is a tower defense video game developed and originally published by PopCap Games for Microsoft Windows and Mac OS X systems. The game involves a homeowner using many varieties of plants to repel an army of zombies. The homeowner, along with a neighbor called Crazy Dave, must defend the homeowner's house during day or night, in the front yard and the backyard (which contains a swimming pool), and even on the roof. It was first released on May 5, 2009 and made available on Steam on the same day.[3][8] A version for the iPhone operating system was released in February 2010, and an HD version for the iPad[9]). An extended Xbox Live Arcade version introducing new gameplay modes and features was released on September 8, 2010.[6] PopCap has also announced a Nintendo DS version, to be released in January 2011, that will feature content unique to the platform.[10] Furthermore, both the original Windows and Mac version of the game have been re-released with additional content in a Game of the Year version. The game received a positive response from critics, and was nominated for multiple Interactive Achievement Awards, alongside receiving praise for its musical score.