Exclusive to the Nintendo Gamecube, Mega Man Network Transmission is a Mega Man Battle Network spin-off. Unlike the rest of the MMBN series, Rockman EXE WS aside, Network Transmission is a 2D platformer akin to the Classic Mega Man games. However, it incorporates many of Battle Network's elements, including Battle Chips, Sub chips, and MegaBuster Power-Ups.
The game is an interquel, taking place between the first and second Battle Network games. It features Japanese voice acting, which is unfortunately left intact in the game's international releases.
In Network Transmission, players take control of Mega Man.EXE. Mega Man, with the help of his Operator Lan Hikari, must navigate "Cyberworld" while fending off Viruses and defeating malicious Net Navis. Unlike the Battle Network RPGs, the player never takes direct control of Lan; in fact, the "real world" is only used to save the game, access Higsby's store, and select the stage that Mega Man will enter.
Like Classic Mega Man, Mega Man.EXE can run, jump, slide, fire his MegaBuster arm cannon and, after a certain power-up, charge the Buster to create a stronger shot. The amount of punishment that Mega Man can take is determined by his HP, which can be restored with health pick-ups and extended with HP Memory power-ups. Mega Man is destroyed if he has no HP, falls through the bottom of the stage, or touches a massively-damaging obstacle (like spikes or lava). Mega Man will be permanently deleted if he is destroyed with no "Backups" remaining, and the player will lose any unsaved progress.
Although the MegaBuster is Mega Man's trademark weapon, it is much weaker in Network Transmission and, in its initial state, requires dozens of shots to defeat a virus. However, Battle Chips are much more powerful. These card-like weapons allow Mega Man to access a variety of weapons, barriers and other miscellaneous powers. Lan can carry twenty unique chips at a time in his Folder. Extra Battle Chips are randomly dropped from viruses, and can also be bought at Higsby's store.
As soon as the stage starts (or whenever Mega Man is rebooted from a deletion), the Custom Screen appears. This allows the player to choose up to five Battle Chips to send to Mega Man. Once Mega Man has received the chip data, the player must wait for the Custom Gauge (located at the top of the screen) to refill before he or she can reopen the Custom Screen. If the player does not load Mega Man with five chips, they will gain extra Battle Chips to choose from upon reopening the Custom Menu. (For example, if three out of five chips are loaded, the number of Battle Chips available on the Custom Menu expands by two.)
Technically, activating a Battle Chip uses it up; however, unlike the original Battle Network games, spare copies of a Battle Chip essentially serve as ammo. Therefore, if the player has collected twenty "Cannon" chips, Cannon can be used twenty times before it becomes unavailable. Each Battle Chip has a unique duplicate limit.
Battle Chips are further balanced by Memory Points. The MP Gauge appears next to MegaMan's HP and essentially functions like the Classic games' Weapon Gauge. Each Battle Chip has its own MB rating, which is subtracted from Mega Man's MP when used. The MP Gauge slowly regenerates over time, but heavy usage of powerful attacks will force the player to wait until Mega Man has freed up enough memory to use another chip.
Power-UPs boost the capabilities of Mega Man's Buster. There are three categories, Power, Rapid, and Charge. Power increases the damage of Buster shots, Rapid decreases the wait time between shots, and Charge first enables Charge Shots, then improves their potency and charge time.
The Armor system also returns from the first Battle Network. Fire, Aqua, Elec, and Wood Armor decrease the damage that Mega Man takes from attacks that aren't of their weakness. (Aqua douses Fire, Elec electrocutes Aqua, Wood grounds out Elec, Fire burns Wood)