Similar to its predecessor, Borderlands 2 is a first-person shooter with elements drawn from role-playing video games. Four playable character classes are available in the base game, each with their own unique Action Skill: Axton, "the Commando", can summon a turret to provide offensive support. Maya, "the Siren", can "phaselock" enemies by trapping them in a sphere of energy for a few seconds. Zer0, "the Assassin", can temporarily become invisible and spawn a hologram decoy to distract enemies. Salvador, "the Gunzerker", can use his titular ability to temporarily dual-wield weapons. Action Skills have a cooldown time during which the player must wait before they can use the skill again. Similarly to the original, completing the main story campaign unlocks "True Vault Hunter Mode", a New Game Plus which increases the difficulty of the game by making enemies stronger, improves the probability of finding rare and higher-quality items, and allows the player's character to reach level 50.