The gameplay in Mega Man X4 is similar to the previous installments of the Mega Man X series. The player is presented with a series of action-platforming stages that can be cleared in any order desired. In these stages, the player must avoid obstacles like falling debris and spikes, and destroy enemy robots to reach the end of the stages. The player character retains the capabilities from previous entries in the Mega Man X series like dashing and scaling walls. Some levels contain ridable vehicles such as hover bikes and armored-mecha. Each of the eight initial stages contains one Maverick boss, and defeating this boss gives the player a new ability. Every boss is weak to a particular ability, adding an element of strategy to the order in which the player completes the stages. New to Mega Man X4 is the ability to play through the game either as X or Zero proper (while Zero was available for play in Mega Man X3, he was limited to being essentially a spare life for the player). The two characters cannot be switched during a playthrough. Though both of them go through the same stages, they operate differently and are challenged differently from the terrain. X wields the "X-Buster", a plasma cannon on his arm that he uses to attack foes from a distance. It can be charged to fire stronger shots. A new weapon is given to the player with each boss defeated while playing as X. These weapons have limited ammunition, displayed by a meter next to one's health, both of which can be refilled by picking up power-ups dropped by destroyed enemies. In some stages, the player can find hidden capsules that contain armor upgrades that greatly enhance X's capabilities. Zero is more melee-oriented than X by using a "Z-Saber" sword. The Z-Saber's power and accuracy compensate for its lack of range; this offers the player a different form of challenge against bosses. Rather than acquiring weapons from the bosses (with the exception of his Giga Attack), Zero learns special techniques such as the "Hienkyaku" air-dash and "Kuuenbu" double-jump. However, Zero cannot upgrade any of his body parts in this game. The player character's maximum health can be extended by obtaining a "Heart Tank" in each of the eight stages. Two "Sub Tanks" can also be found, which can be filled with life energy and then be used to replenish the player's health at any time. Two new Tanks have been added: a "Weapon Tank (W-Tank)", which fills up special weapons; and an "EX Tank", which increases the character's default lives from two to four whenever the player continues from a save point.