on vehicular combat. Gameplay focuses on the "Golden Triangle of Halo": players utilize weapons, grenades, and melee attacks, which are available to a player in most situations. Players may dual-wield some weapons for additional firepower, forgoing the use of grenades and melee attacks. Unlike previous installments, the player's secondary weapon is visible on their player model, holstered or slung across the player's back. Halo 3 introduces support weapons, cumbersome two-handed weapons that slow the player when carried, but offer greatly increased firepower in return. In addition to weapons, Halo 3 contains a new class of gear called equipment; these items have various effects, ranging from defensive screens to shield regeneration and flares. Only one piece of equipment can be carried at a time. The game's vehicular component has been expanded with new drivable and AI-only vehicles. Halo 3 contains non-gameplay additions, such as Forge, a map-editing tool. Forge enables players to insert and remove game objects, such as weapons, crates and vehicles into existing multiplayer maps. Almost all weapons, vehicles, and interactive objects can be placed and moved on maps with Forge. Players can enter Forge games and edit and manipulate objects in real time. A budget limits the number of objects that can be placed. Players may also save up to 100 films of gameplay to their Xbox 360's hard drive, viewing the action from any angle and at different speeds. Halo 3 offers a form of file sharing, where items such as saved films, screenshots, and custom variants can all be uploaded to Bungie's official website. Anyone can browse user created content that has been uploaded to Bungie's website and tag it to automatically download to their console next time they sign into Xbox Live on Halo 3. Modes Halo 3s story or campaign mode can be played alone or cooperatively with up to three other players via Xbox Live or System Link. Instead of each player being an identical character in cooperative play, as in previous Halo games, the first player plays as Master Chief, the second player as the Arbiter, and the final two players controlling the Covenant Elites N'tho 'Sraom and Usze 'Taham. Each player has identical abilities, although their starting weapons vary. Hidden skulls found on each level cause changes to the gameplay when enabled, such as giving the enemies extra health, changing in-game dialogue, or modifying AI behavior. These skulls, as well as