Life bar

Health is an attribute assigned to entities within a role-playing or video game that indicates its state in combat. Health is usually measured in hit points or health points, often shortened as HP. When the HP of a player character reaches zero, the player may lose a life or their character might become incapacitated or die. When the HP of an enemy reaches zero, the player might be rewarded in some way.

Any entity within a game could have a health value, including the player character, non-player characters and objects. Indestructible entities have no diminishable health value.

Health might be displayed as a numeric value, such as "50/100". Here, the first number indicates the current amount of HP an entity has and the second number indicates the entity's maximum HP. In video games, health can also be displayed graphically, such as with a bar that empties itself when an entity loses health (a health bar), icons that are "chipped away" from, or in more novel ways.

Dungeons & Dragons co-creator Dave Arneson described the origin of hit points in a 2002 interview. When Arneson was adapting the medieval wargame Chainmail (1971) to a fantasy setting, a process that with Gary Gygax would lead to Dungeons & Dragons, he saw that the emphasis of the gameplay was moving from large armies to small groups of heroes and eventually to the identification of one player and one character that is essential to role-playing as it was originally conceived. Players became attached to their heroes and did not want them to die every time they lost a die roll. Players were thus given multiple hit points which were incrementally decreased as they took damage. Arneson took the concept, along with armor class, from a set of a naval American Civil War game's rules.

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