Tranzit is Zombies' new story-based campaign set in an "expansive world" for players to explore. "It's massive," Lamia said, describing an open area game world with interconnected zones. Players will have access to transportation, the fortified bus seen in Zombies mode's first trailer, to travel from map to map. The bus provides players with shelter, Treyarch says, "but it's also a confined space, so it comes with its own issues." Players will be able to fight on the bus as it transports the team. They'll also be able to get off the anti-zombie bus, "go out into the fog" to explore, and search for items and new dangers. Also new is Grief, a new competitive mode that pits humans versus humans versus zombies — nicknamed "4z4" mode by Lamia — in a last team standing battle for survival. In Grief, players can't directly shoot each other to kill the opposing team, Lamia says. Only zombies can take out a team of humans. "But you can make their lives harder," he teased, adding that the mode is built on the foundation of "griefing" player-harassment game mechanics that give it its name.