INTRODUCTION
Games handle life and death in a variety of interesting ways, but there are four main mechanisms that are especially common:

* Shields
* Health
* Lives
* Continues

Not all of those are present in all games (in fact, it would be quite rare for a game to include all four), and there can be a lot of overlap between health and lives in particular, as many games will include one but not the other.
This article first describes these mechanisms, and then goes on to provide examples from a fairly random assortment of games.



MECHANISMS

SHIELDS
This includes the kind of shield used by medieval knights and the kind used by spaceships in sci-fi games.
Shields typically offer protection only from certain angles or types of attack, and absorb damage which would otherwise reduce the player's health. If the attack is from a different direction or the shield strength has been depleted, health will be lost as usual.
Often, shields will gradually regenerate. Some games include both shields and armour, which function in exactly the same way, except that shields regenerate and armour does not.
Shields are often represented as items which may be bought or found, unlike maximum health which is typically either static or related to experience.


HEALTH
This is the most basic measure of a player's "aliveness". Many arcade games dispense with it altogether, meaning that any damage at all is fatal and causes the player to lose a life. In addition to combat damage, it's often possible to lose health as a result of interaction with the environment (eg. sharp spikes), or when other resources run out (time, fuel, food, water). In some cases the player may be instantly killed, such as when falling off a cliff.

It's usually possible to regenerate lost health using one or more of the following:

* resting
* items (potions/medikits/hearts/etc)
* magic (healing spells)
* special locations (shrines/inns/towns/etc)
* special characters (clerics/repair-bot/etc)
* special attacks (vampires/etc)
* completing the level

In some cases health may only be regenerated under certain conditions - for example, trolls might not be able regenerate health lost to a fire-based attack.
Often, a player's health will affect their ability to perform certain actions. This is especially common in games which use component/limb-based damage, where damage to an arm might prevent the player from holding a weapon in that hand or wielding a two-handed weapon; similarly damage to the engine of a tank might prevent it from moving.
In addition to recovering lost health, it's often possible to increase the player's maximum or base health during the course of a game. This may occur when the player "levels up" by gaining experience, or when they find special items, or at certain scripted points in the story. Similarly, there may be some types of enemy which are capable of lowering not just the player's current health, but also their maximum health.
When the player's health is reduced to zero, the player is killed (or knocked unconscious etc). In some cases, they will simply lose a life and be allowed to continue as if nothing had happened. In other cases, the penalties may be the same as those listed in the next section...


LIVES
Obtaining extra lives tends to difficult (items which bestow additional lives are normally well hidden or given as rewards for completing a particularly tough challenge), and the consequences of running out of lives are often serious - for example:

* continue (see below)
* game over (aka permadeath - no second chances allowed)
* restart from last savepoint, with or without penalties such as lost experience/gold/items (may be earlier on in the same level; may be the start of the level; may be several levels back; may even be the start of the game)
* reload a saved game (may be limited to specific savepoints, or the player may be allowed to save at any point).


CONTINUES
Continues allow the player to gain another set of lives and keep playing where they left off. The concept originated in arcade games, where the player would have to insert more money in order to continue, which boosted profits for the arcade operator. In modern PC and console games, continues are mainly limited to arcade-inspired titles. In some cases, using a continue prevents access to special bonus stages or reduces the player's score.



EXAMPLES

THE LEGEND OF ZELDA
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ImageMany of the mechanics listed previously are present in Zelda. The player carries a shield which deflects ranged attacks from one direction only. They initially have a maximum of three health points (represented by hearts) but this can be increased by finding special heart container items. They can also find other items and visit special locations in order to restore lost health. Furthermore, there is a powerful ranged attack which the player may only perform while at full health.

ImageThe player may use unlimited continues, or load a saved game.


SUPER MARIO BROS.
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ImageAt first glance, it would appear that there is no health system in Super Mario Bros - only lives (which can be gained by collecting a green mushroom). However, when Mario is transformed into Super (big) Mario it gives him the ability to survive one hit from an enemy. It could be argued that Mario does have two different states of health - at full health he can breaks blocks; at low health he can fit through small spaces (much like Link's special sword throw attack being available only when he's at full health in The Legend of Zelda).
Something similar applies to certain enemies too - at full health parakoopas can fly, but after sustaining damage, they lose their wings and become regular koopatroopas. In many other arcade games, the bosses will also change their behaviour or attacks as their health is reduced, so it's definitely not something that's limited to player characters.


UFO : ENEMY UNKNOWN
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ImageThe X-Com games use a complicated mix of health meter and limb-based damage (plus stun damage and unconsciousness, psionics and of course zombification by the awesome Chrysalids).
Initially, a single shot is nearly always fatal, and it's only after the player has researched body armour and medikits that the damage system really comes into play. Body armour protects the wearer by absorbing a varying portion of the damage, depending on the direction of the attack. The remaining damage will reduce the wearer's health.
However, there's also the possibility that the character will sustain a "fatal wound" to one of six body parts. These do not cause immediate death, but they do cause a further reduction in health each turn, until they are treated using a medikit (representing the effects of blood loss etc). They also affect the character's ability to perform certain actions. For example, in the screenshot, the character has suffered one fatal wound to the head, and because of that his firing and throwing accuracy are both massively reduced. In addition, he will die in three turns, as he has just three health left (3 health divided by 1 fatal wound = 3 turns). Had he been wounded in the leg instead, the character's accuracy would not have been affected, but his movement speed would be greatly reduced.

ImageThe only way to revive a dead soldier is by reloading a saved game. Soldiers are expendable and casualties are inevitable - especially early in the game before body armour and medikits are available, and late in the game when the aliens start using more destructive weaponry such as blaster bombs.


AVENGING SPIRIT
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ImageAvenging Spirit is fairly unusual in that the player character is already dead at the start of the game (the player assumes the role of the eponymous spirit) - however, that doesn't mean they're invulnerable.
In this game, the player must possess enemies, and use them to move around and attack other enemies (depending on the type of enemy possessed, the player will be able to use different attacks, have different jump strength, etc). However, the bodies have limited health, so it is possible for them to be killed.

ImageIf the player is killed while possessing another character's body, the spirit must leave the body. Unfortunately, the spirit can only survive outside of a body for a short time (shown using an "energy" bar).
If the player runs out of energy before they can possess another enemy, then it really is game over - but as Avenging Spirit was originally an arcade tile, the player has the option to continue. Powerups are scattered throughout the game which restore both health and energy.


ZELIARD
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ImageThe health system in Zeliard is quite conventional, but with a few intersting touches. The player carries a shield which provides limited protection from the front only. As the shield only protects the upper body, the player must crouch in order to block some types of attack. Also, unlike in The legend of Zelda, the shield itself has hitpoints (shown in the bottom right in the screenshots). Replacing a broken shield is extremely expensive, but repairing a damaged shield in a town is very cheap, which adds a nice element of strategy.
There are of course the usual healing potions and locations (churches which are free, and inns which cost money). Alternatively, the player can regain lost health simply by standing still inside a dungeon (it's possible to increase game speed so this takes less time, provided a safe location can be found where monsters won't appear).

ImageWhen the player dies, they are transported back to the first town in the game. They lose any carried money etc, but their achievements are not lost - bosses remain dead, doors remain unlocked, etc.
Alternatively, the player may reload a saved game. Saving is allowed only at the sage's hut in each town - the sage also performs other functions such as offering tips and levelling-up the player when they have gained sufficient experience. In addition, there is a special item which can be used to instantly transport the player back to the last sage visited, which allows them to avoid a lot of back-tracking without losing any progress (very useful in emergencies).


RIVIERA : THE PROMISED LAND
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ImageThis game is quite unusual in that the player is not penalized for losing battles - quite the opposite in fact. If the player loses, they may immediately retry, except that the enemies will now start with reduced health and the player will have a partially filled power meter, making the battle easier.
It also featured a "practice" mode, where the player could fight battles to gain experience without suffering any negative consequences at all. Unfortunately, this added an element of grinding, as the player needed to fight a lot of tedious practice battles in order to able to beat tougher opponents in the main game. Reviewers were generally critical of both features.


MONUMENTS OF MARS
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ImageAs with many early arcade style games, the player does not have a health meter so a single hit is fatal.

ImageAgain, as was common in games of this type, death merely forces the player to restart from the beginning of the current screen (this happens automatically), and they have an unlimited number of lives. It's also possible to reload a saved game (the game can be saved at any point).


THE SECRET OF MONKEY ISLAND
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ImageThe Secret of Monkey Island avoids the issue of life and death by making it virtually impossible to die. It even includes one famous scene where the player can fall off a cliff, at which point a fake "game over" screen is displayed - only for their character to bounce right back up, after landing on a rubber tree! The only place in the entire game where it is possible to die, is when the player is stuck underwater - and even then they have 10 minutes in which to figure out what to do (plenty long enough to try every possible action).


ROGUE
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ImageThis game uses the usual health bar and the usual potions & items to boost stats. It also introduces hunger, which forces the player to eat regularly in order to stay alive. In addition, there are certain monster types that can reduce the player's maximum health or lower their experience level (having the same effect).

ImageRogue is perhaps most famous (or should that be notorious?) for introducing "permadeath" (a defining characteristic of the "roguelike" genre). When the player dies in Rogue, it really is game over - they are forced to start a new game completely from scratch. While it is possible to save a game in order to take a break and be able to resume play later on, the file can only be opened once, so death is still permanent.
This system is often unpopular as it is extremely unforgiving, and it's often subject to abuse (by creating backup copies of savegame files etc). However, fans of the game assert that it makes the player more attached to their character and think more carefully about taking risks.


WING COMMANDER
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ImageThis game includes quite a detailed damage system. The player's ship has front and rear shields, as well as armour on all four sides. The shields regenerate, but this requires energy which is also drained when the player fires their guns, adding an element of strategy. Additionally, the ship can sustain component-based damage - for example, the weapon tracking computer may be damaged so that guided missiles won't work; or the energy generators may be damaged so that shields regenerate and guns fire more slowly.
A nice touch is that damage is visible from the cockpit and during the landing sequence at the end of a mission.

ImageIf the player is killed during a mission it's game over - they must reload a saved game. However, the player also has the option of ejecting or can return to base without first completing the mission objective, and this generally isn't penalized too harshly, although it will affect future mission selection. Also, if the player's wingman is killed during a mission, they will usually have to fly solo for a while.


ADVANCE WARS
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ImageIn Advance Wars, health represents the number of individual vehicles/soldiers in a unit. Because of that, the amount of damage a unit can inflict upon the enemy is directly proportional to its health. Also, as all vehicles of any one type are fungible, it's possible to join two damaged units to create a single healthy unit. Alternatively, units may be repaired at friendly cities, bases, etc. Later games in the series introduce special mobile repair units. Finally, one of the available player characters (a CO called Andy) has a special ability which repairs damaged units.

ImageIndividual units are generally expendable. The only way for the player to lose is by allowing their HQ to be captured, or by allowing all their units to be destroyed and factories captured - in which case they may simply restart the mission or reload a saved game.


CRITICAL MASS
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ImageShip design in Critical Mass is completely modular, and performance is determined solely by the components used. For example, thrusters increase either acceleration or turning ability depending on where they are positioned, while scanner units increase a ship's detection range. There are shields which absorb damage on whichever side they are placed, but once a missile hits an unprotected side, damage is distributed at random among the internal components.
Because these components cease to function once damaged, a ship's damage level can seriously affect its performance (note in the screenshot, how the damaged ship has a lower "Turn" stat - that's because six of its thrusters have been destroyed).
There is no health bar as such, but instead, there are the most important components of all - command centres. Once all those have been destroyed, the whole ship will explode. Although most premade ship designs only have one or two command centres, it's possible to design incredibly durable custom ships with many more (plus repair bots which slowly repair damaged components).

ImageThe player is only directly responsible for the control of one ship (wingmen are expendable). If that ship is destroyed it's game over - Critical Mass uses "permadeath", so there are no lives or continues and it's not possible to reload from a previous savepoint. However, if a mission is going badly, it's possible to avoid being killed by either flying off the edge of the map (friendly wingmen will continue to fight), hyperspacing (there is a delay of several turns, during which the player is still vulnerable), or in extreme cases by ejecting (can be risky as ejector pods are destroyed in a single hit, and it also reduces the likelihood of being awarded a medal).