Where there is no light, there is darkness. Darkness reduces the search rate by 10% in general and gives a -5% accuracy hit chance for all attacks. The Night Vision Vampire skill allows the player, if they are currently a Vampire, to ignore both of those debuffs.
Darkness also allows Humans to hide more easily and to remain well hidden; while instead it allows Vampires to hide and to remain hidden.
Both in Serling and Twilight City, the sky is always perpetually dark and clouded. As such, only some of the outdoor areas are lightened up by surrounding light sources, provided the Power Plant is active and running.
Inside buildings, lights can be switched on and off. The lights can be turned on if the Power Plant is active and running or if there's a Generator set up and running inside the building, otherwise even if turned on there won't be any light.
In certain dungeon areas like The Sewers, the Sub-Level Z and the Quarantine Zone and in certain tiles like Fields, Cornfields or Beaches there's no electricity or lightning at all and as such there's no light whatsoever.
Here are explained how light affects the Vampire's search rate for hiding players:
Lights on, Night Vision and Sharpened Senses: 1 search roughly to detect.
Light on, no Night Vision, Sharpened Senses: 3 searches roughly to detect. (No sharpen case will be 5.725)
Light off, no Night Vision, Sharpened Senses: 13 searches roughly to detect.
Light off, no Night Vision, no Sharpened Senses: Varies.
Human players can set up one Generator (which can be found at Hardware Stores) inside each of any non-dungeon buildings in order to be able to turn the lights on if the Power Plant is currently offline. In order for it to work, it needs to be filled up with Gas Cans (which can be easily found outside Gas Stations). Every 5 minutes tick (6:30, 6:35, 6:40,...), the generator's fuel level is decreased by 5.
Each Gas Can adds 60 points to the generator's fuel level for a maximum of 240, which equals to 4 hours. As such, the generator can be filled up with a maximum of 4 Gas Cans, upon which it'll be completely full.
Upon flipping the building's breakers off, the Generator will also be automatically turned off and won't waste any fuel for the time being. If the Power Plant is up and running, instead, even with lights on the Generator won't use up and waste any fuel.
Status Message (Generator OFF/Generator ON)
It is Empty.
Barely any fuel / It is running low on fuel
Half tank / It is running on half a tank.
Nearly full tank / It is running on a nearly full tank.
If players accidentally find one or more hiding players through searching, they'll be automatically unhidden and will remain as such until they hide again or until the player(s) who found them log(s) out. If the previously hidden player is successfully attacked even just once, they'll always remain unhidden until they hide again even if the other player logs off.
If a player hides somewhere but there are other active players already hidden before them in or on the same tile or bulding, as long as they don't log out, they'll always be able to see the newly hidden player as present as if they were unhidden.
Hiding isn't possible at all if there are other players currently unhidden in or on the same tile or building, no matter if they are online or not.
While hiding is possible if there's one or more NPCs in or on the same tile or building, if hostile, this can cause them to grow suspicious and prompt them to search for the player in order to attack and kill them, which may or may not occur. If that happens, the player will remain unhidden until they hide again, and will potentially be killed by the NPC. As such, it's suggested not to hide in presence of hostile NPCs.
Performing certain actions, such as crafting, healing themselves, reloading or using the walkie talkie don't automatically unhide the player; while instead performing other actions such as closing or opening the door, flipping the breakers on or off, searching or saying something, do automatically unhide the player.
Zombies can play dead anywhere. Since Zombies can hide everywhere, it's suggested not to play dead inside of a building since Vampires can use the Supernatural Senses skill and end up accidentally detecting the player. As such it's suggested to play dead only outside of buildings or on empty tiles.
Upon playing dead Zombies appear as dead corpses to every other player and NPC until discovered through searching, which means they can be dumped if inside of a building, fed on or used to defile the spraypainted messages. However, they cannot be revived with Injectors.
Zombies cannot hide if other players are on or in the same tile or building and are active.
Humans can only hide inside buildings and cannot hide if other players are inside the same building.
Hiding can fail. The success on finding an hiding spot is influenced by the ruin level of the building and by the lightning, chances getting lower if the lights are on or/and if the building is severely dilapidated.
Hiding Humans can be found much more easily if the lights are on.
If the player dies, detection is disabled until they stand back up.
If a certain building is more than lightly barricaded, there is an high chance that there are players currently hiding or hanging out inside the building or that the building is one of the previously mentioned relevant ones. Although, many others instead prefer to hide in buildings with open doors, lights off and no barricades at all in order not to attract too much attention.
If the player is close to some barricades or fences and they are being set up or attacked by another player, the first player can detect who or what is doing so.
If any noise is made inside any building, Unlike the Smell Rot or Track Prey skills, the noise range will be reduced by one. Whether listeners are inside or outside doesn't matter.
If players successfully manage to hit an NPC, the NPC may cause some noise upon counter-attacking or dying.
Every 5 minute tick in game any hostile NPC will attack any player in the same tile. Whether or not the attack succeeds, is up to the RNG.
Friendly NPCs may help out the players in various ways, actively or passively, such as attacking other players or NPCs hostile also to them, by setting up some light barricades on a building, by damaging a building or even by reviving them.
Allows the player to reveal any hiding human players in or on the same tile or building through searching.
Supernatural Senses (Vampire's skill)
At the cost of 1 AP, allows the player to know how many players or/and NPCs are currently present or hiding inside or outside any building and non-building tile. If the player is outside or inside an heavily or extremely heavily barricated building, the player won't be able to sense anything inside or outside. If the player possesses also the Discerning Palette skill, the report will be in the format of "You sense the presence of [A+B+C+D] beings outside. [A] of them seem pleasantly familiar. [B] of them seem unpleasantly familiar. [C] of them seem less intelligent than most." [A] are the number of players in your friends list or your group or members of allies of your group, [B] are the number of players in your enemies list or members of enemies of your group, [C] are the number of NPCs and [D] are the number of players who are not in your friends list, enemies list, your group, members of allies of your group and members of enemies of your group or in other words, strangers. Otherwise, the player will only be able to distinguish between NPCs and players.
Smell Rot (Passive) (Zombie's skill)
Passive. Gives the player the coordinates leading them towards the closest active Zombie players and NPCs in the area. If a zombie NPC is in range, it will be in the format of "You smell especially heinous undead funk". If a zombie player is in range, it will be in the format of "You smell heinous undead funk".
Track Prey (Passive) (Vampire's skill)
Gives to the player some approximate coordinates leading them towards the last NPC or player who attacked them or who they attacked, if still alive. If the weather is not clear, detection ranges and results may be different.
Discerning Palette (Passive) (Vampire's skill)
Allows the player, by using the Supernatural Senses skill, to know how many hostile players or/and NPCs are currently present or hiding inside or outside any building and non-building tile.