Resident Evil Zero (or Resident Evil 0) is a survival horror video game developed and published by Capcom for the GameCube in 2002. It is a prequel to Resident Evil (1996), covering the ordeals experienced in the Arklay Mountains by special police force unit, the S.T.A.R.S. Bravo Team. The story takes place in July 1998 and follows officer Rebecca Chambers as well as convict Billy Coen as they explore an abandoned training facility for employees of the pharmaceutical company Umbrella. The gameplay is similar to other Resident Evil games, but adds the ability to switch between characters to solve puzzles and use unique abilities. Development for Resident Evil Zero began for the Nintendo 64 in 1998. The partner system was created to take advantage of the short load times possible with the capabilities of the Nintendo 64 Game Pak. The cartridge format also provided limitations, as the storage capacity was significantly less than that of a CD-ROM. The team had to approach the design differently from previous series entries to conserve storage space. Resident Evil Zero was designed to be more difficult than previous Resident Evil games. Inspired by Sweet Home (1989), the team removed the item storage boxes present in earlier games and introduced a new item-dropping feature. Production was switched to the recently unveiled GameCube after development slowed due to memory storage issues. Only the concept and story remained from the original game, which had to be rebuilt. Resident Evil Zero received generally positive reviews. Critics praised the graphics and audio for building a haunting atmosphere. Opinions on the new partner and item systems were mixed. Some found the changes were an improvement and added new layers of strategy; others believed the changes were cumbersome or non-innovative. The controls were panned as outdated and Capcom was criticized for not evolving the series' tank controls. The game was ported to the Wii in 2008, and a high-definition remaster was released in January 2016; the rereleases received mixed reviews due to lack of improvements. Resident Evil Zero was commercially successful, having sold over 4 million copies across all platforms.