HardHead

HardHead (ハルドボルズ) is a virus from the Mega Man Battle Network series. It resembles a cannon with an armored head and does not move from its position. When its mouth is closed, the virus is in a guard state. In the first Mega Man Battle Network game, while in this state, HardHeads are invulnerable to all attacks. However, the introduction of guard-breaking chips in Mega Man Battle Network 2 makes it possible to damage them while their mouth is closed, in this and all later games. Before attacking, HardHead's head will wobble, and then its mouth will snap open and reveal a small cannon in its throat. HardHeads will then shoot out a cannonball flying to and landing on the panel which the player was standing on, prior to the cannonball's release. When the cannonballs land, they break the panels they fall on.

While these viruses had no elemental attribute in the first and second games, in the third one, HardHead2 and HardHead3 became fire and water attributes respectively. As a result, in Mega Man Battle Network 3, HotHead's cannonball turns the panel it lands on into a lava panel and ColdHeads's cannonball leaves the panel it lands on frozen. While theses viruses did not make an appearance in the games following Mega Man Battle Network 3, their attack is available in the form of a retro Battle Chip, "Ball", in Mega Man Battle Network 4. The chip returns in the last two game installments, once again named "Cannon Ball."

HardHead
HardHeads are gray when closed. When open, they become red with yellow eyes.
 * HardHeads are invulnerable to non-breaking attacks while their mouth is closed. Their heads shake just before they open their mouth, dropping their guard and launching one cannonball, aimed directly at the panel the player is standing on. After the attack, their mouth clamps shut and they regain the guard status once more. The cannonball attack will destroy the panel it hits.
 * In Battle Network 2 and 3, the attack gains Guard-breaker status and can punch through MegaMan's defenses if he tries using a shield or Guard chip.

HardHead2/HotHead
HardHead2s are yellow when closed. When open, they become red with yellow eyes.
 * Just like HardHeads, HardHead2's are invulnerable to non-breaking attacks while their mouth is closed. Unlike their weaker variant, HardHead2's have a much faster firing rate and shorter rest period between attacks. They only appear during storyline battles in the first two Battle Network games.
 * In Mega Man Battle Network 3, this virus becomes HotHead, a Fire-attribute virus capable of shooting cannonballs at a very fast pace. Its cannoballs no longer destroy panels, but change them into Lava panels on impact. Unlike, the first two games, in Mega Man Battle Network 3, HotHeads can be encountered outside of story-related battles.

HardHead3/ColdHead
HardHead3s are light-blue when closed. When open, they become red with yellow eyes.
 * HardHead3s are invulnerable when their mouth is closed. They have the fastest firing rate of the HardHead variants in the first Battle Network game. Like HardHead2, these viruses only appear in story-related battles. In the second game, although rare, HardHead3's can be fought outside story-related battles.
 * In Mega Man Battle Network 3, this virus variant becomes ColdHead (コルドボルズ), an Aqua-element virus that shoots cannonballs with the power to change panels to Ice. Also, in this game, ColdHead became the second and thus weaker variant, than HotHead, which became the stronger of the two. As a result, ColdHead's firing rate has grown slower than HotHead's.

HardHeadΩ
HardHeadΩs are forest green when closed. When open, they turn blue with pink eyes.
 * HardHeadΩ is the strongest variant of HardHead, with a large amount of HP and a highly damaging attack power. Unlike the weaker variants, HardHeadΩ barely rests in between cannon blasts and can pockmark the player's side of the field in mere moments.

Trivia

 * While in the first and second Mega Man Battle Network games "ColdHead" was the third and strongest variant of the virus family, in Mega Man Battle Network 3, "HotHead", originally the second variant, became the third variant, with ColdHead taking its place and becoming the second.