As the player character, Recker, the player can use two campaign-only functions: the Engage command and the tactical binocular. The Engage command directs Recker's squadmates, and occasionally other friendly units, to attack any hostiles in Recker's line of sight. The tactical binocular is similar to a laser-designator, in the sense that it allows the player to identify friendly and enemy units, weapon stashes, explosives, and objectives in the field. By identifying enemies, the player can make them visible without using the visor, making them easier to mark for their teammates. At one point, Recker will briefly lose the tactical visor, forcing them to only use the Engage command to direct his squadmates on a limited number of enemies. The campaign features assignments that require specific actions and unlock weapons for use in multiplayer upon completion. Collectible weapons return along with the introduction of collectible dog tags which can be used in multiplayer. Weapon crates are found throughout all levels, allowing players to obtain ammo and switch weapons. While crates hold default weapons, collectible weapons may be used whenever they are acquired and level-specific weapons may be used once a specific mission assignment has been completed by obtaining enough points in a level. "Battlefield 4"s multiplayer contains three playable factions—the United States, China, and Russia—fighting against each other, in up to 64-player matches on PC, PlayStation 4, and Xbox One (24-Player on Xbox 360 and PS3). A newly reintroduced "Commander Mode", last seen in "Battlefield 2142", gives one player on each team a real-time strategy-like view of the entire map and the ability to give orders to teammates. Also, the Commander can observe the battle through the eyes of the players on the battlefield, deploying vehicle and weapon drops to "keep the war machinery going", and order in missile strikes on hostile targets. A spectator mode is included, enabling players to spectate others in first or third person, as well as use a free camera to pan around the map from any angle. On June 10, 2013, at E3, DICE featured the map "Siege of Shanghai", pitting the People's Liberation Army against the U.S. Marine Corps. The gameplay showcased Commander Mode; new weapons and vehicles; and the "Levolution" gameplay mechanic. The video displays the last of these at various points, including: a player destroying a support pillar to trap an enemy tank above it; and a large skyscraper (with an in-game objective on the top floor) collapsing in the center of the map, kicking up a massive dust cloud throughout the map and bringing the objective closer to ground level.