||This article may contain original research. (March 2008)|
Health is a game mechanic used in tabletop role-playing games and video games to give value to characters, enemies, NPCs, and related objects. This value can either be numerical, semi-numerical as in hit/health points, or arbitrary as in a life bar.
Hit points 
Hit points, also known as health points (or HP), damage points, heart points, life points, or just health (among other synonyms), is a finite value used to determine how much damage (usually in terms of physical injury) a character can withstand. When a character is attacked, or is hurt from a hazard or fall, the total damage dealt (which is also represented by a point value) is subtracted from their current HP. Once their HP reaches 0, the character will be unable to fight. In role-playing games, health is often abbreviated as "HP".
In some role-playing games such as Dungeons & Dragons, a player character's hit points are determined by character level. The hit points of monsters are decided by rolling "Hit Dice". Characters with high constitution will have an advantage when hit points are assigned. A character whose hit points are reduced to zero is considered dead or incapacitated. Other games sometimes lack levels, hit points, or both.
In certain editions of the game, player characters with 0 HP are not dead, but rather knocked unconscious. Within the range of -1 and -9, they are considered to be mortally wounded and dying, and their HP will steadily drop until it is stabilized. At -10, the character dies. Depending on the rules, a character who suffers 50+ points of damage from a single blow may die as a result of "Death from Massive Damage". The player must then make a "saving throw" of the dice in hope of countering the damage. Failure to do so results in the characters dying, regardless of their remaining HP.
In many role-playing video games, the objective is to deplete the hit points of enemies while maintaining the health of player characters. Hit points can typically be refilled by using a restorative item, staying the night at an "inn", or utilizing healing magic. Generally, characters are killed or rendered unconscious as soon as their hit points reach 0.
Hit points represent a method of determining the vitality of, or resistance to death or destruction, of a being or object (some versions of Dungeons & Dragons, for example, include hit point values for objects, weapons, armor, even doors and walls, allowing players to attack and destroy them.) Rather than realistically model damage as it would exist in real world situations, hit points give an abstract idea of how much damage, in game terms, something can withstand until it is destroyed completely.
An example would be the comparison of a serious, but non-lethal, wound. A person who has taken a serious sword wound might not be in danger of immediate death, but might lose the usage of a limb or some mobility as a result. In the same situation in most games, a character that suffers such an injury would lose hit points; as long as they are still above zero, however, the character would not have diminished performance capacity. Contrarily, as a single assault from a weapon could kill a perfectly healthy person, a single attack against a healthy game character using a hit point system often does not result in death.
Some games do penalize the player for his or her character taking damage. Several of The Legend of Zelda games, for instance, allow the main character to use a projectile attack, but only at full hit points. Paladin's Quest has both magic powers and life energy using hit points as a resource, and thus a sufficiently damaged character may not be able to safely cast some spells.
Generally, the usage of hit points avoids the complexities of having to model the effect of damage to various body or mechanism parts, although some games rely on this as part of the strategy inherent to combat. Many of the MechWarrior games give each body part of a mecha its own hit point allotment, and damaging or destroying individual parts has an adverse effect on the way the mech operates, despite not outright destroying it. The Fallout series of games allows targeting a specific body part, which results in not just damaging a foe's hit points, but also possibly crippling a limb or even blinding the foe.
Some games that do not usually employ this mechanic may do so in some circumstances; the beholder and hydra of Dungeons & Dragons have separate body parts, and destroying them individually plays into the strategy of fighting that foe.
Dungeons & Dragons co-creator David Arneson described the origin of hit points in a 2002 interview. When Arneson was adapting the medieval wargame Chainmail to a fantasy setting, a process that with Gary Gygax would lead to the game 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 so 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 given multiple hit points which were then incrementally decreased. Arneson took the concept, along with armor class, from a set of a naval American Civil War game's rules.
Life bar 
A health or life bar is used to display a character's health in many video games. A typical life bar is a horizontal rectangle which begins full of color. If damage is taken or mistakes are made, the colored area gradually reduces (some also change color, typically from green to yellow to red, as health is reduced). When the bar is completely emptied, the result is game over (death, being knocked out, etc.). In 1984, both the arcade game Dragon Buster and computer game Gemstone Warrior first used a bar to represent "health". Punch Out!! was released earlier the same year and also has a health bar, and Star Trek - Strategic Operations Simulator was released 2 years prior and also has a segmented life bar. There have since been many variations on the life bar:
In Street Fighter and other fighting games, the bar does not instantly immediately decrease when damage is taken. Instead, an area representing the damage is marked in red, and the health lost quickly drains away. This is useful in assessing the amount of damage caused by an attack.
Some video games also feature a recharging health bar. In these games, the player character cannot usually take as much damage as a player with a traditional life bar, but health regenerates over time (usually initiating regeneration when the player avoids being damaged for a period of time). Notable examples of this are the Hydlide series, Ys series, Halo series, Call of Duty series, Destroy All Humans!, Gears of War, Tom Clancy's Rainbow Six Vegas, Tom Clancy's Splinter Cell Double Agent, and Red Steel. Some games may increase the maximum health limit of the player character as they progress through the game like Paper Mario: Sticker Star.
Icon-based health 
Icons are another method for measuring health. Some games such as Prince of Persia, DuckTales, and Mr. Nutz, which use a number of icons to represent health units; every hit against the player character will always decrease health by one icon or unit at a time. In other games a hit may reduce health by one icon or unit, a fraction of one icon, or many icons at once, depending on how powerful the hit is, and the strength of the character's defense of armor. In most of the games in the The Legend of Zelda series of video games, the player's health is represented as small hearts. Weak attacks against the player will take only a fraction of a heart, usually one-quarter or one-half, and stronger attacks may take many whole hearts at once. Several games make use of similar heads-up displays. Super Mario Bros. 2 uses small red icons (in 16-bit versions of the game, they're changed to hearts) in the top left corner to designate how many hitpoints the player has remaining, and Bram Stoker's Dracula uses small flasks of liquid. The game Minecraft uses Hearts to display Health, like Legend of Zelda, but damage will not reduce quarters of a heart, rather, the minimum is half a Heart, but attacks can drain multiple hearts, depending on damage and player's armor.
Other games, such as Deus Ex, show a HUD of a human body, which is green to begin with. As the player takes damage, the respective region of the body turns yellow, orange, red, and eventually disappears altogether. For the head and torso, this is fatal. For arms, this causes a significant decrease in weapon accuracy or damage (or a complete inability to use them), while such a damage for legs usually leads to a badly impaired movement. A similar system, but showing the player's current vehicle rather than a human body, is used in some simulation games such as Rogue Squadron.
Other variations 
Recharging health 
||This section needs additional citations for verification. (May 2011)|
Some games use a system of recharging health (or regeneration), where health points are regained over a short period of time (usually minutes). This mechanic has its origins in Roguelike games of the 1980s. In the 2000s, the mechanic was popularized among first-person shooters by the Halo series, while action RPGs such as Fable have continued to utilize the mechanic.
Other games require the use of healing spells, skills, or items (such as potions, medicine, first aid kits, bandages, syringes, medical bags, herbs, and even food) to regain health. Many game systems incorporate both slow regeneration and instant-effect healing skills and items. Games often have items that recharge all or some of a character's health, but they may differ in that, some games allow the player character to collect and carry many items in an inventory and use them to recharge health at a later time when needed; while in other games the player character cannot carry items in such a way and items will recharge health immediately upon touching them or sometimes upon picking them up. If such health recharging items are carried, the player usually needs to manually select the item and use it before their health completely runs out. Some games however contain items that, when carried, automatically revive a character when their health reaches zero and restores them to either full or part health.
Another common way of replenishing health in games is to have a number of fixed locations that characters can travel to, and where their health will be replenished either for free, or by paying some in game currency. These facilities can usually be used an unlimited number of times, and themes such as resting at an inn or character's home or base, drinking from a fountain, visiting a hospital or other medical facility, or visiting a person or location that heals with magic have all been used across different games and genres.
An increasingly common standard, is a complete lack of any health-replenishing items—the wounded player is simply expected not to take damage by taking cover and wait (generally from 5–20 seconds) as his or her character recovers. Most of these games do not feature a health meter; the player judges his or her health from blood on the screen, heavy breathing, and other details.
Incremental health 
In the Sonic the Hedgehog series, the player character collects rings, which are usually used as his or her health indicator. They are shown as numbers at the upper left side of the screen. Whenever the player character takes damage when he or she does not have a shield, all of the player's rings scatter in many directions. If the player is fast enough, the player can reclaim some of the rings before they flicker and disappear. However, if the player character possesses a shield and takes a hit that the shield is not invulnerable against, the shield is lost and the player character will keep all of his or her rings. Almost all of the player characters can be killed instantly if they do not possess any rings or a shield when they take any damage. Sonic's rings differ from most health mechanisms in that having multiple rings offers no extra protection; however many rings a player possesses, all will be lost with one hit. However, some newer Sonic games such as Sonic Blast, Sonic the Hedgehog, Sonic and the Secret Rings, Shadow the Hedgehog and Sonic Unleashed have the player lose only a set number of rings per hit (usually ten or twenty), meaning that having more rings provides better protection.
Percentage meter 
In the Super Smash Bros. series, instead of health bars featured in most fighting games, percentage meters are used. When attacking an opponent or being attacked by an opponent, the percentage meter rises based on the damage inflicted; as the percentage meter increases, the character gradually becomes easier to knock away with strong attacks, possibly getting knocked out of the arena and, thus, losing either a life or a point, depending on the mode of play. In the Stamina mode, health percentage is used. When the characters fall off the stage, they are disqualified from the battle.
Health represented without Heads-Up Display 
In order to immerse the player in the gaming experience, some developers do away with the health bar (and other on-screen displays) completely and try to present a character's health in other ways, such as showing a character limping or displaying visible wounds when they are injured. Jurassic Park: Trespasser (1998) has no HUD and represents its player character's (Anne) health as a heart-shaped tattoo on her breast which fills up with red as the damage increases. When she dies, the heart has a chain around it. In the early Resident Evil (1996–present) video games, health is shown both with the player character limping and pressing his/her wounds in pain, and with an EKG display in the inventory screen. Games such as Call of Duty 2 (2005) or Peter Jackson's King Kong: The Official Game of the Movie (2005) have no life bar; instead, the game uses the screen as health, and when the player gets hit, the screen flashes red, and in some games the vision will also becomes blurred in this condition (more damage indicated by a deeper red coloration). In some games, characters slouch over and breathe heavily as a result of low health when left idle; blood stains or wounds may also appear on characters to show they are injured. Some third-person games such as RoboBlitz (2006), Dead Space (2008) and Ghostbusters: The Video Game (2009) have health bars shown on the player model rather than in a HUD. They resemble ordinary health meters apart from being physically attached to the character's equipment.
See also 
- Massive Damage Threshold and Results. The Hypertext d20 SRD. Retrieved on 2008-3-24.
- Allen Rausch. "Dave Arneson Interview.". GameSpy. 2004-08-19. Retrieved on 2008-3-24.
- "Gaming's most important evolutions". GamesRadar. Oct 8, 2010. p. 4. Retrieved 2011-03-29.
- Chris Antista. "The 10 most creative life bars. (page 2)". GamesRadar. 2010-08-17. Retrieved on 2010-8-19.
- Szczepaniak, John (7 July 2011). "Falcom: Legacy of Ys". GamesTM (111): 152–159 . Retrieved 2011-09-07. (cf. Szczepaniak, John (July 8, 2011). "History of Ys interviews". Hardcore Gaming 101. Retrieved 6 September 2011.)
- Kurt Kalata & Robert Greene. "Hydlide". Hardcore Gaming 101. Retrieved 2011-05-01.