Mega Man X4

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. Some levels contain ridable vehicles such as hover bikes called Ride Chasers and mechs called Ride Armors.

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.

Mega Man X4 takes place in an ambiguous year in the 22nd century (21XX), where humans coexist with intelligent androids called "Reploids". A second Maverick-hunting group has been formed to supplement the Maverick Hunters, though its relationship with the humans is tenuous. The army, called the "Repliforce", is a military regime led by the giant Reploid General and his second-in-command, Colonel. The storyline differs slightly depending on whether the player chooses X or Zero.

In the game's introduction, the Sky Lagoon, a massive floating city, is attacked by a Maverick and sent crashing down onto the city below it, killing countless humans and Reploids. At the crash site, Zero rescues Iris, Colonel's kind-hearted sister, who was caught in the mayhem but is unharmed. X and Zero then encounter Colonel, suspicious of his presence, and attempt to bring him back to Maverick Hunter HQ for questioning. Colonel denies Repliforce's involvement in the Sky Lagoon destruction, and refuses to disarm out of pride. The Repliforce thus begins a movement to claim independence from the human government and create a nation for Reploids only.

Originally, the Mega Man X3 team had no plans to provide a sequel until their superiors from Capcom aimed to try the X series on new hardware. The team aimed to make Zero different from X, he was remade as a proper samurai-like warrior who wields a Z-Saber instead of shooting like X. In order to get the approval to make Zero playable, the developers gave him special moves based on the Street Fighter fighting game series to compensate for lacking X's powers. In particular, Capcom struggled in the beginning with the number of backgrounds they had to draw, but were pleased with results.

There were twice as many sprite animation patterns to create. Since there was too much data creating the player characters, they had to employ a compression routine to store it all, and divide the stages into two sections. Designing X's armors proved difficult since the character looks different depending on which parts the player obtains first.

Reviews for the PlayStation and Saturn versions of Mega Man X4 have been generally positive. Critics praised the added option to play through the game as either X or Zero, noting that the drastic differences in the way the characters played the same levels added to the game's replay value. However, most of the same critics concurred that Mega Man X4's 2D side-scrolling gameplay was tired and overdone well before the game was released. In particular, GamePro and Next Generation both gave it mixed reviews on the sole basis of its perceived lack of series innovation; GamePro asserted that "the gameplay's none removed from Mega Man for the NES - things are just a little bigger and a little louder," while Next Generation suggested that those interested in the game should instead "pick up Mega Man X3 in the used bin for a third of the price, since you won't miss much."

However, a different GamePro critic reviewed the PlayStation version and gave it a resoundingly positive review, calling it "an impressive 32-bit debut" and "a definite must-have for any action gamer's library." GameSpot took more of a middle ground, concluding that "All in all, a few more 3D effects would have been nice, but the decision to stick with a true 2D environment is bold, if somewhat outmoded. Aesthetically, Mega Man X4 is a sizeable improvement over its predecessors, but you must remember that it's only a side scroller."