Health and Damage

Overview

While a less significant mechanic than most other first-person games, players in Portal 2 have a hidden health value that can be decreased by a handful of sources, leading to the player's death if it reaches zero. This generally only happens if a player takes sustained damage, as the player's health quickly recovers to full when not taking damage. The health and damage mechanics are identical in all modes of play (single player, cooperative, full game, challenge mode etc.), assuming no mods are in use.

Health Mechanics

The player's maximum and default health value is 100. If the player has not taken any damage for XXX time, they will recover YYY health every ZZZ interval until their health is fully restored.

Not all forms of death interact with health. Death triggers will kill the player on contact regardless of their current health value - fields of these are what causes the player to die when they fall into "bottomless pit" areas, and are also used for effects like neurotoxin (a death trigger field is spawned when the timer runs out, killing the player if they are inside it).

Damage Sources

Damage sources reduce the player's health by a defined amount. There is no cooldown between instances of damage, and multiple sources can damage the player at the same time, killing them more quickly (e.g. being shot by multiple turrets).

Goo

Goo (also known by other names, e.g. acid, toxic water) is first encountered in the Chapter 1 map Cube Momentum in single player / the Course 0 map Calibration in cooperative. Goo normally seems like certain death, as once a player makes contact with it, most levels offer no way to escape and recover. Despite this, goo actually deals XXX damage at YYY intervals, meaning a player can swim in goo for up to ZZZ time before dying.

One place where goo can be swam in and survived is Finale 1. If the player jumps towards the faith plate bouncing the cube, they can swim into one of the corners of the faith plate while looking at an upward angle and climb onto the platform, letting them recover from the damage. It is faster however to bunnyhop all the way to the platform, and goo swimming is currently not used in any speedrun routes. Swimming in goo is used in some full game least portal routes, but these routes acquire damage immunity first, rendering goo damage mechanics irrelevant.

Turrets

Turrets are first encountered in the Chapter 3 map Turret Intro in single player / the Course 3 map Turret Walls in cooperative. They are the most common source of survivable damage in the game, and completing actions quickly before taking lethal damage (which acts like a timer) is a common technique in many speedrun and least portal routes. This includes exploiting the "wakeup" and "sleep mode" cycles that turrets have.

When a valid target enters a turret's vision (usually a player), they perform a wakeup animation that includes locking onto the target. This animation takes XXX time from being triggered to the turret opening fire. A turret deals XXX damage at YYY interval, meaning a player can survive fire from a single turret for up to ZZZ time before dying. Taking fire from multiple turrets will divide this time accordingly. If a turret loses sight of all valid targets for XXX time, it will perform a sleep mode animation that lasts YYY time. A turret cannot fire during this animation or interrupt it, meaning that waking up a turret, leaving its vision, then re-entering its vision just as its sleep mode starts gives a player more time before taking fire, as the turret must complete its sleep mode animation, then perform a wakeup animation.

Damage Immunity Glitch ("Betsrighter")

Include explanation of mechanics, execution and uses.