[[quoteright:350:[[VideoGame/JakAndDaxter http://static.tvtropes.org/pmwiki/pub/images/Jak_n_Daxter_lurker_fish_5974.jpg]]]]
[[caption-width-right:350:Samos said ''not'' to swim to the island.]]

-> ''"It is pitch black. You are likely to be eaten by a Grue."''
--> --'''''VideoGame/{{Zork}}'''''

Videogame developers are responsible for producing ways to keep the player from wandering away from the game world. Now, assuming you don't have to deal with PlayerCharacters that can fly, you have dozens of options that would fit into a game world: an InsurmountableWaistHeightFence, BottomlessPits, minefields, or even just running out of dry land.

However, there are some combinations of environment and PlayerCharacter special abilities where none of the above are plausible options. For instance, how is the game supposed to stop a character from swimming out into the open sea if he lacks SuperDrowningSkills?

Enter the Border Patrol, a monster or other hazard introduced specifically to prevent the player from wandering too far without resorting to the immersion-breaking InvisibleWall[[note]]There probably is an invisible wall, it's just too far out to reach before the Border Patrol stops you[[/note]]. This often takes the form of an InvincibleMinorMinion that you can't move past, a TheBrute style enemy that you have to run away from, or an obvious environmental hazard that you can't survive. In some games the Border Patrol monster can actually be killed, though it's likely to [[RespawningEnemies respawn]] if the game designers anticipated your violent yearning to be free. When done well, the player is chased away by the dangerous thing and returns to the field of play. When done badly, the player character is unavoidably killed by the whatever, occasionally suffering from CutsceneIncompetence as a monster just [[DropInNemesis wanders over to the player and instantly kills him]]. A type of BrokenBridge. Can be NightmareFuel if unexpected. If it returns you to a particular location when it catches you, it's also a MookBouncer.

Naturally, savvy (and glitch-happy) gamers just ''[[SincerityMode love]]'' [[ScriptBreaking figuring out how to get around these.]]

See also BeefGate, where you are expected to be able to bypass the monster, but not right away. {{Metroidvania}} games measure your progress by what sorts of environmental hazards you can bypass.

----
!!Examples:

* Each of the ''JakAndDaxter'' games featured one: a lurker shark, a perimeter defense robot, and a purple tentacle respectively.
* ''VideoGame/RatchetAndClank'' also uses hungry fish in areas with water you're ''not'' supposed to be in.
* Similar to the examples above, ''VideoGame/{{Gothic}} II'' has a friendly shark come a-calling when the hero tries to swim too far from the island chain he starts on.
* In a desert area of ''SpaceQuest'', there was a patrolling sand worm that would instantly eat you if you wandered away from where you were supposed to be. Gamers who misinterpreted this as a puzzle spent some time trying to kill the sand worm by various means.
** Also, if you go to a certain screen, a meteorite falls on you.
** Go out of bounds outside the Deltaur, and the defenses will blast you into space dust.
** Ditto for ''SpaceQuest III'', where there's a snake that eats you if you wander off course.
** And ''VideoGame/LeisureSuitLarry'' and the goon in the alleyways, as well as the taxis whenever you try to cross the road.
** Sand worms play a similar role in one level of ''Franchise/StarWars [[VideoGame/DarkForcesSaga Jedi Academy]]'': they'll try to eat you no matter where you go, so long as the path taken involves walking on the sand.
** And, heck, many Sierra adventure games pulled variations on this theme. [[VideoGame/KingsQuestV King Graham]] could find himself [[http://www.youtube.com/watch?v=S_Vz5rcqNL4#t=06m50s sailing straight into the maw of a sea monster]]. Not to mention the general perils of swimming in oceans.
** ''VideoGame/KingsQuestVI'' [[JustifiedTrope justified the trope]] by explaining that so few people ever found the Land of the Green Isles because of dangerous currents surrounding them. Looking at the sea draws a warning of dangerous undertow, and getting your feet wet immediately starts suspenseful music; go a decent bit further and the undertow gets you.
** Averted, however, in ''VideoGame/KingsQuestIII'', where there is no border patrol, but the desert to the west is simply endless (as is the ocean to the east, but that will cause you to drown rather quickly).
* Since you could only drown if you were underwater, ''VideoGame/{{Half-Life 2}}'' upgraded the alien leeches from the first game and placed them in water near coastal areas. They start out causing little damage, but the number of leeches increases the further you swim out, creating a sort of exponential damage curve that makes it impossible for you to survive to reach the edge of the map or skip parts of the level.
** Since buyers of the game also gain access to the Source SDK, you can see specifically how this border patrol is managed. The entity used to enforce the border is literally called "trigger_waterydeath".
** In a handy bit of ScriptBreaking, spawning the Airboat via console allows you to avert this entirely.
** ''DearEsther'', a Source Engine mod turned stand-alone game, has voices that whisper "Come back" if you swim out to sea. You drown and respawn if you persist.
*** Prior to any loading screens happening in the original mod, the voice (or narrator) would whisper "Come back".
* In [[GangplankGalleon Treasure Trove Cove]] in ''{{Banjo-Kazooie}}'' you ''could'' kill Snacker the shark (who prefers one-liners to one-hit kills). He respawned after a short period of time, though.
** But Treasure Trove Cove still needed an InvisibleWall, because that was one of the levels that allowed Kazooie to take flight.
*** Poetically, it was the level where Kazooie learned to fly in the first place. Areas such as Clanker's Cavern, Freezeezy Peak, and Click Clock Wood also allowed for flight, but those areas were more "naturally enclosed" than Treasure Trove Cove was, and thus they didn't have such a need for invisible walls. Moreover, Treasure Trove Cove tantalized the player with valuable items that were placed in the ocean, right where Snacker the shark swims.
* Nepto, encountered early in ''VideoGame/FinalFantasyIII''. Realistically, you can only beat him if all four of your characters are in the game's Infinity Plus One class, which you won't have at this point without cheating. You can resolve your Nepto problem by other means -- and you'd better, because you can't run if you start the fight.
** There are two other examples in the game: Bahamut is encountered early in the game (and you have to run), but you can then encounter him again shortly afterwards, and he will find new ways to destroy you (he prevents you from getting to a specific cave). You have to play through ''most of the game'' before you can take him on and beat him (in order to get him as a summon). The other example is Leviathan, who patrols a lake near the game's starting point. Much like Bahamut, he will murder you in his sleep for most of the game, until you're actually powerful enough to beat him (and thereby get to the underwater cave ''he'' guards).
* Similarly, ''VideoGame/FinalFantasyVII'' has the Midgar Zolom, which impedes your progress early in the game by devouring you if you try to cross a swamp. It's possible to avoid it by baiting it into a corner and sneak around, or you can save and reload every time you see the Zolom approaching, which will cause it to respawn away from you. It's even possible, with grinding and the right strategy, to slug it out with him,[[note]]Although if you ''do'' manage to kill the Midgar Zolom, it just respawns at an out-of-view part of the swamp and runs right at you again. Killing one is possible. Killing two in rapid succession is very difficult.[[/note]] but the game wants you to catch a [[HorseOfADifferentColor Chocobo]] and just outrun the thing.
* In a very specific example, the Guardian from ''VideoGame/FinalFantasyVI'' is invincible and won't let you into the Empire's headquarters. You have to run away, though you can fight it again much later and win.
* In ''VideoGame/FinalFantasyV'' you encounter a ruined castle about halfway through the game [[spoiler:in Galuf's world.]] Attempting to go in right away will, unless you have done some serious LevelGrinding, get you quickly and horribly killed by a monster called the Shield Dragon. This is particularly annoying if you did not save beforehand. [[spoiler:But since said castle contains the game's {{Infinity Plus One Sword}}s, this makes sense.]]
* ''VideoGame/{{Xenoblade}}'' has the non-monster variant. There is nothing to limit how far you can swim in the ocean surrounding The Fallen Arm, but go too far and you'll run into Ether-polluted water that drains your health VERY quickly.
* In ''VideoGame/{{Crysis}}'', if you swim out too far from the lovely North Korean/alien infested island, you get devoured by a HUGE shark. Not kidding. Try it.
** Also there are ships that can see you from a mile away the moment you walk out of the game's borders and, get this, fire missiles at you. Yeah.
** If you somehow avoid the shark and the enemy battleship, your own superiors will vaporize you with your suit's killswitch for straying outside the mission area.
* ''VideoGame/{{Okami}}'' has the crazy water dragon. It is actually possible to bypass the water dragon using the lily pad brush power, but damned if it's not really, REALLY difficult to do.
** As the story progresses, the dragon became less of a problem with the help of Orca, who was faster than the dragon (and immune to its attacks anyway). Later on the dragon [[spoiler:is killed]], allowing the waters to be traversed safely.
* Speaking of dragons, there's ''VideoGame/WithinADeepForest'', which has a Sky Dragon that will eat you if you try to cross islands, and a cat that will eat you for your powers. [[spoiler: You can eventually avoid both. The Dragon is gone in the cold, bleak future, and the cat won't eat you if you get the ball that has NO power.]]
* ''FarCry'' has the player get one shot killed by a helicopter that appears, when normal helicopters take at least 4 seconds of constant fire to kill him.
* ''Cauldron 2'' on the ZX Spectrum had invincible lethal bats which prevented you leaving the castle in which the game was set.
* ''VideoGame/SkiFree'' has extremely fast [[BigfootSasquatchAndYeti Yeti]] that chase after and eat you if you travel too far in any direction.
** Though it is possible to outrun by [[http://xkcd.com/667/ pressing f]].
* ''VideoGame/WorldOfWarcraft'' uses a combination of border patrols and triggered effects. Most of the coasts are patrolled by elite sharks, and if you swim past them you get a "fatigue" debuff that kills. Prior to the ''Cataclysm'' areas that had not been fully implemented would apply a "no man's land" debuff that teleported explorers out and "Guardians of Blizzard" that death-touched the over-eager.
** The sharks can be avoided by walking on water or by being high-level enough to kill them, but the fatigue debuff is unavoidable; [[TheDevTeamThinksOfEverything Even player ghosts succumb to it.]]
* In ''VideoGame/GrandTheftAutoSanAndreas'' and ''Grand Theft Auto IV'', players who try to skip ahead to the other cities before the plot grants them access (indicated by literal Border Patrols - the bridges to these cities will be closed off and some cops will be standing behind the boundary) will find themselves suddenly slapped with a '''six-star wanted level''', and usually be gunned down by police and/or U.S. Army helicopters shortly thereafter ([[BlatantLies I was just going for a swim, officer, honest!]]) They'll continue to chase you even if you go back into an open zone, but at least there you can access unlocked Pay 'n' Sprays and safehouses to help you lose your wanted level.
* In ''VideoGame/GrandTheftAutoV'' flying too far out to sea, or piloting a boat too far out to sea, will cause the engine to cut out and, if in a boat, the vehicle to sink. If swimming you are more likely to be killed by a shark than reach the map edge.
* In ''Mercenaries'', the edge of the map is designated a restricted area, and staying there too long (about five seconds) triggers a barrage of missiles from "Allied Command" that is impossible to avoid and does enough damage to kill you instantly, even if you're driving a tank when it hits.
** It is possible, however, to doge the rockets. It takes a lot of luck and one of the Russian Mafia's twin-bladed combat helicopters from the second map area. You have to wait until they start firing, then spin the helicopter backward between the rockets. If you avoid them, you're free to fly until the second wave comes a few seconds later. If you survive again (say, using the godmode cheat), you'll run into an invisible wall.
* ''VideoGame/ScarfaceTheWorldIsYours'' has a shark eat Tony whole if he swims too far out. Boats are easily available, though you're shit out of luck if your boat happened to explode in the middle of the ocean and you survived the blast because you knew that shark was coming...
* In ''VideoGame/BeyondGoodAndEvil'', there are occasional barriers than can be bypassed, ''Zelda''-style, with various upgrades to the hovercraft. However, attempting to cross the farthest-out barriers results in a warning, followed by non-damaging shots that blast you back within the borders of the area.
** It is, however, possible to bypass them with glitches - and drive more than half an hour to make the screen turn black and [[WrapAround make you reappear on the other side of the map.]]
* Some of ''VideoGame/{{Halo 3}}'''s multiplayer maps had this. For example Sandtrap takes place in a large desert map with no apparent barriers other than a few posts sticking up. You're more than welcome to cross past them but once you do, explosions will start happening all around you, almost always resulting in instant death. However if you are driving a fast enough vehicle, you can actually outrun the explosions, making for a quite entertaining race. Eventually however, you will come across an InvisibleWall.
** The Mythic maps added some more instances of this trope in Sandbox. Much like Sandtrap, obelisks will gun you down once you cross the warning borders. The only real difference is that the walls at the end of the level are visible. However, [[spoiler:there's a hidden skull in the death zone. You can pick it up is by going into Forge (the level editor) and building an explosion-proof tube. Alternatively, with practice, you can dodge the blasts while in monitor mode, allowing you to move a teleporter out to the skull for pickup after you die.]]
** There's also the turrets of Snowbound. While nowhere near as powerful as the ones in Sandbox, they are quite deadly. Again though, you'll come across an InvisibleWall if you manage to bypass it [[spoiler:Hint; put a bubble shield over it or yourself.]]
** Certain campaign levels, as well as multiplayer levels have invisible instant-kill barriers that prevent you from going out of bounds or shortcutting. ''VideoGame/HaloReach'' also has an out-of-bounds timer that requires you to "Return to the Battlefield" in [[StalkedByTheBell 10 seconds]] or die.
* ''VideoGame/BetrayalAtKrondor'' had this in some places that were supposed to be inaccessible for the particular chapter you were playing. This was a case of "you can kill them, but they respawn instantly" (the game at least was fair and warned you if you clicked on the enemies that "there are too many of them, we can't beat them").
* The first level of ''VideoGame/PrinceOfPersia2'' has a lame example of this: walking to the right on a certain screen in the first level will lead to a SoundOnlyDeath.
* The Chicken Island levels in ''VideoGame/TakAndThePowerOfJuju'' are surrounded by water inhabited by ElectricJellyfish.
* In ''VideoGame/MassEffect1'', straying beyond the boundary of the current planet you're exploring (roughly one square kilometer) you'll get a radio call from your ship's navigator that you need to turn back. If you keep going though, you get picked up and dropped back off at the starting point.
* The old ''MotocrossMadness'' games for the PC had some kind of invisible BorderPatrol, and they came packing some [[{{BFG}} serious heat]]. Maps were usually cordoned off within Insurmountable Valleys...except, for a [[{{Determinator}} determined]] player, they ''were'' surmountable. If you managed to climb up and ride more than a few feet into the vast flat wastelands outside the valley, you would get [[BlownAcrossTheRoom blasted away]] by an invisible cannon, and then comically plummet back to the stage to a [[BombWhistle stock "bomb dropping" sound effect]]. Arguably an instance of highly aggressive {{Invisible Wall}}s.
** ''VideoGame/ATVOffroadFury'' also used this method of BorderPatrol, as well as all of the other games in the Unleashed saga and beyond.
* From ''VideoGame/{{Zork}}'': It is pitch black. You are likely to be eaten by a grue. A simple solution to prevent would-be adventurers from stumbling about in the dark, rather than finding the light source they were supposed to. The earliest versions of the game featured bottomless pits in which you could stumble. However, it was an imperfect solution as they would appear in illogical areas, like a darkened attic, while not being present in the lit room below it. This is referenced in ''ZorkZero'', the chronologically earliest game in the series, which starts out using bottomless pits, but eventually you manage to seal the bottomless pits forever -- driving out the grues inside and creating an even worse menace.
** A ShoutOut to this occurs in ''TheJourneymanProject'': If you walk up the pitch-black maintenance transport tunnel, the tram runs you over, and the HaveANiceDeath screen says "Well, at least you weren't eaten by a grue!" Also, if you wander anywhere you're not supposed to be, you will be spotted by humans and captured.
* Every ''VideoGame/{{Battlefield}}'' game has a commanding officer instruct you to return to the battle or you will be shot for being a deserter, after 10 seconds you'll take fast constant damage until you either die or return to battle. Especially diabolical if you do this in an transport aircraft or aircraft carrier and doom all of your teammates too.
** This was actually used as a griefing tactic in Battlefield 2, mostly to allow the pilot of an attack helicopter to kill the gunner only, by pointing just the gunner (who sits in front) on the edge of the border, waiting for them to die then picking up the friend you wanted to be the gunner.
** In ''VideoGame/BattlefieldBadCompany'', when crossing the map border, you receive a radio message that enemy artillery is active in this area. Although it makes less sense after the squad [[spoiler: goes AWOL]].
* Similarly, ''VideoGame/StarWarsBattlefront'' has some guy either warn you that deserters will be shot ([[FridgeLogic even if you're]] ''[[FridgeLogic the Emperor]]'') or just say "Get back to the battle!" Unfortunately, you just die instantly, rather than slow draining health as in the above example.
* The various ''MechWarrior'' titles have enforced a similar system, with two lines (orange and red) visible on your radar. Crossing the orange line triggers a warning; crossing the red one triggers explodey death.
* ''VideoGame/{{Spore}}'' includes a giant sea monster that will swallow you whole during Creature phase if you try to swim too far out into the ocean, even if you're flying a hundred feet above the water. There used to be a glitch where you'd start the phase in the ocean and get eaten whenever you tried to swim to land..
** Also, in the cell phase it's possible to get a ''[[http://www.youtube.com/watch?v=Gi3kPswDQks huge]]'' cell attacking you. Whether or not this is a glitch or some form of border patrol isn't known.
* In ''Return Fire'' if you fly your helicopter off the edge of the map you hear a sonar sound followed shortly be a submarine surfacing beneath you which fires a heat seeking missile that never misses and is a one hit kill. It can, however, be dodged infinitely.
* Zelda-like ''Sphinx and the Cursed Mummy'' featured the water-surrounded city of Abydos. Since Sphinx can swim, however, they filled the water surrounding him with [[PsychoElectricEel electric eels]] that made the water [[SuperDrowningSkills an insta-kill.]] Oddly, the HubLevel is ''also'' water-surrounded, but ''doesn't'' do anything about it--you just hit an InvisibleWall.
* The 8-bit-era wireframe game ''Cholo'' was set in a post-apocalyptic world, and venturing into an area where the radioactivity level was too high for your shielding would cause your droid avatar to take damage over time. You guessed it: the edges of the (square) map were ''highly'' radioactive. (As a point of interest, by using the aeroplane or leadcoat droids, you ''could'' get over the edge of the map before receiving terminal damage. Whereupon, you would wrap around and appear on the other side of the map.)
* ''Might And Magic IX'' had an example after a ship wreck with tons of sea serpents that not only swarm if you swim towards them would shoot at you while you were at the shore making running away the only practical option.
* The Sea-doo racing game ''Splashdown'' features giant squids which grab your racer and fling him crashing back towards the map if you wander too far.
* Commissars will shoot you dead in the Soviet campaign of ''VideoGame/CallOfDuty'' if you run from the battle.
** In addition, several levels in the ''VideoGame/CallOfDuty'' series were lined with minefields around the combat zones. In one level set in Cherynobyl, wandering off the path would result in getting hit by a 'lethal pocket of radiation.'
* Straying too far from the main area in the text adventure ''[[BigApplesauce New York]]'' [[{{Gangsterland}} will get you murdered.]]
* ''VideoGame/{{Fallout 3}}'' features this trope when trying to get into [[spoiler: Vault 87]] - the only way there is a roundabout path through [[spoiler:Little Lamplight]]. If you try to take the direct route there, you'll find out the hard way the door got hit straight-on by a nuke, and start absorbing ludicrous amounts of radiation - as high as 3,000 rads/second (for comparison, taking increments of 200 rads will weaken your skills, and exceeding 1,000 rads is fatal - meaning you can die by ''standing around for 0.3 second.'' This is ''the'' single most irradiated place in the whole series) It turns out that this is all for naught, too. Even if you have enough Rad-Away and Rad-X to nullify and reduce radiation, the way to your destination is blocked by an [[LockedDoor inaccessable door]].
** In the original ''VideoGame/{{Fallout|1}}'' you took damage from dehydration if you wandered off too far without stopping at known locations, unless you carried water flasks. The second game in the series dropped the idea, but still had powerful random encounters near late-game areas. In both games, the entire world map was accessible to you the moment you left the starting location, so some system (easily subvertible with enough knowledge and/or luck) was necessary to prevent too early exploration and diverging from the intended path.
** The Old World Blues DLC for ''VideoGame/FalloutNewVegas'' features forcefields around the Big MT Complex that will teleport the player back if they go past.
*** In Dry Wells, unlocked by nuking Legion territory with the Lonesome Road add-on, there is a crater where one of the missiles hit, entering this area causes instant death via kill barrier (rather than near-instant death by radiation).
*** The main game combines this with {{Beef Gate}}s, where if you wander off the plotted line at a low level, you'll be massacred by DemonicSpiders such as Deathclaws, Cazadores, Radscorpions, or Nightstalkers.
* In ''VideoGame/{{Prototype}}'', trying to cross one of the bridges to the mainland will get you bombarded by an off-screen air raid. However, trying to cross in the water will inexplicably stop your air powers from working and then jump you back to the land for no discernible reason (they give what would be a plausible reason not to be able to cross the water, but it would only make sense if the water ''killed'' you.) Also, trying to use the helicopter to get out will result in a warning to turn back and then getting blown up.
** It is possible to dodge the bridge's air raid long enough to reach an invisible wall. If you try to just swim away from Manhattan without using the bridges or vehicles then you'll also meet with an InvisibleWall.
** In addition, trying to get to the Reagan aircraft carrier before it comes into play in the story (only possible with a hammer throw) will lock the Reagan's rather powerful cannons on you. These knock you back substantially and will one-shot you if you don't have the upgrade that puts you in overdrive upon death.
** The jumping happens in any deep water, for no apparent reason. It also takes the character a few seconds to jump out, even in the ponds and streams of the parks (which can't be the 30-40 feet deep that time suggests).
* ''VideoGame/UnrealTournament2004'' will blast you with the Ion Cannon on the more open maps if you go a-wandering. The firing delay means that if you're driving a manta flat-out it's possible to taunt it into firing and only taking survivable splash damage.
* A temporary BorderPatrol can be found in the Lothlórien area in ''VideoGame/TheLordOfTheRingsOnline''. You first have to gain the elves trust to enter their forest. If you chose to ignore the guards warning, you get pincushioned by arrows raining from the treetops the moment you try to cross the small river.
** There's another one on the borders of the Anduin. The only way in or out is by using boats - if you try to swim the river, orc archers on the far side will kill you dead. The boats are gated by a quest chain, so that only those who buy the Mirkwood content can reach it.
** In Angmar, there is a line of Watching Stones that applies quick-killing damage-over-time effects when you cross it. The "wall of death" was a rite of passage for many when the game was released. Like others, completing a quest line will allow you to cross the line.
* In ''FarCry 2'', if you wandered off the edge of the playing area, your character would faint from dehydration, and inexplicably wakes up back within the borders of the map. If you drove off the edge in a vehicle, you'd faint, then [[FridgeLogic wake up within the map's borders with the vehicle missing]].
* As mentioned above, the new ''VideoGame/BionicCommando'' has a tendency to kill you with radiation if actually try to explore the city the game takes place in.
* In ''RuneScape'', you can enter a dark area without a light source if you want to, but you won't be able to see shit, and you'll also be attacked by a horde of unseen tiny insects that rapidly take your health down.
* The first ''{{Mercenaries}}'' game had Allied jetfighters and [[ShoutOut Naboo starfighters]] from ''Franchise/StarWars'' (LucasArts published the game) attack the player relentlessly if he/she tries to swim out of the game's boundaries.
* ''Anime/MobileSuitGundam 0079: Rise From the Ashes'' for the SegaDreamcast used simple common sense: If you left the mission area, so would your team, and [[GameOver the mission would be aborted]].
* ''VideoGame/{{Borderlands}}'' had a BorderPatrol consisting of a warning by the Crimson Lance, warning you that if you go any further, you WILL be bombarded. Going any further results in [[DeathIsASlapOnTheWrist you losing some money and being transported to the nearest New-U Station.]] Many areas have impassable cliffs (up or down) to keep you in. Some also have high-powered looking turrets with double laser sights that lock on to you if you approach the edge.
* ''VideoGame/{{Borderlands 2}}'' also has the Turrets Of Doom in the same way as it's predecessor.
* In ''VideoGame/ResidentEvil'', if you try leaving the mansion through the front door you'll be stopped by a zombie dog that's always waiting there, [[CutsceneIncompetence even though you could just shoot it]].
** The Gamecube remake has one of the dogs enter the mansion if you open the front door, with several more dogs visible outside. After killing the dog that comes into the mansion, your character will refuse to open the front door again.
** ''VideoGame/ResidentEvil2'' has two instances of this. Once you have entered the Police Station property, a group of zombies will be pounding on the gate from the other side. Even if you shoot them through the bars, the game won't let you go back out because it's simply too dangerous to go back out onto the streets. Later on you find another exit (near where you find the valve), but opening the door just lets a handful of zombies inside and won't let you open it again. The implication here is that outside that door there's just ''too damn many'' zombies.
* In ''G-Nome'' players are restricted to within the game area by the Orbital defense kill zone. Should a player wander too far outside, a computer voice will warn the player. If the player continues, the computer will say, "Have a nice day", and the player's mecha will be destroyed by a huge laser blast, presumably from a space-based weapon.
* A Russian FPS ''Truth About the 9th Company'' [[VeryLooselyBasedOnATrueStory reenacts a combat]] that took place in the War in Afghanistan. If you move too far away from the action zone and cross an invisible border, the game abruptly and summarily ends as you are court-martialled for desertion.
* ''VideoGame/TheSaboteur'': Some borders of the map that aren't blocked by mountains or water appear striped on the map and are named as 'War Zones' if you enter them. They do indeed look like battlefields, containing anti-tank barriers, scorched vegetation and ruined buildings. Protrude too far into these zones, and fighter-bombers fly over and drop insta-kill payloads and bullets on you. This is particularly jarring because on any difficulty below '[[{{Oireland}} Feckin' Hard]]' your character can take an inordinate amount of punishment. If you survive this (relatively simple as the bombs are inaccurate), you'll eventually meet an InvisibleWall.
* In ''VideoGame/FreeSpace'', flying too far from the origin on the coordinate grid results first in a message that you are leaving the zone of engagement, then a suddenly self-destructing ship.
* In ''VideoGame/SoldierOfFortune II'''s Colombia levels, if you fall too far behind or go too far ahead of your allies, they will yell "Execute him!" and shoot you dead. Worse, there's a glitch that can get them stuck and make the level {{unwinnable}}.
* The thing outside the front door in ''Videogame/AloneInTheDark1992'', and the Chthonian Worm that blocks the secret passage from the basement (which you need to unlock anyway to get back in later).
* ''VideoGame/PilotWings'': "Stay Inside of Course!" If you keep going, you get "Out of Course" and fail the event.
* In ''VideoGame/IRobot'', saucers patrol the edges of the shooting sections, making it a very dangerous place, should you wander there.
* In ''[[VideoGame/RagnarokRoguelike Ragnarok]]'', the world is bounded by an endless ocean. If you go into it, however, the world serpent Jormungandr appears and gives chase. He is lightning fast, completely unkillable and will one-hit kill you if you come close to him or attack him (even from the other side of the screen, [[TheComputerIsACheatingBastard despite having no ranged attacks]]); the only escape is to rush back into the world proper before he reaches you.
* In the first ''GearsOfWar'', going into dark areas gets you eaten by the Kryll (killer bats). Unfortunately, going through dark areas before the Kryll get to you is ''required'' at some points of the game.
* ''Dead Meets Lead'' is infamous among {{Steam}} gamers for employing ''malaria'' as a deterring agent for players who so much as stray off the beaten path!
* ''VideoGame/CallOfDutyBlackOps'' subverts the usual InsurmountableWaistHighFence or NonstandardGameOver method of keeping players inside the multiplayer or campaign map, respectively, with the "[[UsefulNotes/TheVietnamWar Jungle]]" multiplayer map. The map is surrounded by the aforementioned InsurmountableWaistHighFence, except for one open area (marked with a skull-and-crossbones sign) that leads into a rice paddy. [[TooDumbToLive Ignoring the sign]] and walking into said paddy, however, is a ''[[LandMineGoesClick very bad idea.]]'' To add insult to injury, your death is listed as "suicide".
** However, there aren't actually mines until a few yards in. [[GoodBadBugs Guess where a good place to put a SAM Turret is?]]
* Some levels of the first ''SeriousSam'' game have the player receive sunburn damage when wandering too far into the desert. In ''Serious Sam 3'', open stages are patrolled by a sand whale who eventually comes in handy.
* The original ''AirForceDelta'' features a level involving flight through a large canyon to reach the main target area; flying above the canyon's cliffs would result in a barrage of surface-to-air missiles spammed toward your plane until it's finally shot down.
* ''VideoGame/StarWarsTheOldRepublic'': As with many other [[MassivelyMultiplayerOnline MMOs]], attempting to go outside the map boundaries results in a warning and then gradual damage, in this case in the form of a stacking damage-over-time [[StandardStatusEffects debuff]] that kills you at five stacks (somewhere between ten and twenty seconds). This is occasionally [[JustifiedTrope justified]] by implying that you are heading into a lake/ocean, or that the weather is taking a turn for the worse: on Tatooine a sandstorm kicks up, and on Hoth and Ilum a blizzard appears. In a handful of cases it is necessary to head into these zones to find certain hidden collectibles; usually it's one only needs to traverse a nominal strip intended to fool you into thinking there is nothing there, but at least once you need to come within an inch of your life to claim your prize.
** In the Operation Explosive Conflict (an Operation being an instanced dungeon designed for eight to sixteen people) the group at one point needs to pass through a series of trenches as there is a full-scale battle implied to be occurring in the background. If a player should somehow scale the sides of the trench, an Exhaustion Zone warning will show - and a few seconds later the player will be killed instantly by what appears to be an orbital strike.
* VideoGame/ArmoredCore, since its first iteration, lets you know helpfully where the map boundaries are, even if you do not actually possess a radar. Traditionally, the boundaries have a green line, in which crossing it triggers your onboard alarm system. Cross the red line, you fail the mission. The game treats it as if you have forfeited the mission/battle and thus kicks you out, usually with no penalties, except for storyline-important missions, which do boot you all the way back to the Title Screen. Vertical boundaries are however, a bit vague, and getting Mission Failed from flying too high is an all too familiar problem.
** This rears quite an ugly head in Armored Core 4, in which most of its map boundaries are too restrictive, cf., "A Swarm of Red Eyes" mission, where you have to kill mini drones by the boatload before it reaches a launch station. Not only your room to maneuver is too small, you cannot chase it all the way back to the launch station. Frustration ensues. TO make matters worse, the standard double line markings are replaced by a single line, with two types of alarms. Failure to head back means instant failure, even if you edge just that slightly too far.
** In Armored Core V, the lack of radar means the devs must denote the line somehow. The result is a very obvious yellow-and-black boundary lines which ''kills'' you upon straying too far. The issue with height restrictions still plague the game, as some maps feature buildings taller than the map boundaries (Upper Area/Executive Sector is notorious for this), so continually trying to climb will result in your death. This is not to say that players don't get savvy, but the problem is there.
* In ''VideoGame/MaxPayne 3'', if you wander too far from your principal during an EscortMission, a mook will pop up from nowhere and gun him/her down unceremoniously.
* In the offline version of ''VideoGame/DiabloII'', if you walk out of the area where your current quest is at and try to walk into a new area your character hasn't been told to go to yet, you will be immediately attacked by a large swarm of higher-level creatures. This is especially difficult for the Necromancer Class, as their Summoned Help likes to wander around, sometimes into these dangerous areas, which invariably brings down the wrath of the developers.
* If you go out of the battle zone in ''GhostRecon: Advanced Warfighter'', your HUD starts to get [[InterfaceScrew fuzzy]] and the CO tells you to return to battle. Disobey, and it's Game Over.
* In the ''VideoGame/WaveRace'' series, going outside of the boundary buoys or going out of the water will trigger a countdown. Fail to get back in bounds in time and you will get disqualified (and, if you're playing Championship Mode, a zero for the course).
* Although ''VideoGame/TheLegendOfZeldaTheWindWaker'' has a large, seemingly limitless ocean overworld, the overworld does have its limits. Ordinarily, Link can't sail past set boundaries outside the map (the King of Red Lions, Link's boat, stops and turns around automatically) but if Link swims instead, he can pass the original boundary until he drowns and respawns at the nearest land. However, with cheats, one can have Link swim even farther out...until Link drowns anyway. Yes, even with cheats that let Link swim forever, he still drowns at a set distance that the player cannot reach without cheating. Granted, there's nothing at that distance away from the map, but there's still an insurmountable obstacle that one cannot even reach in normal play.
* In ''VideoGame/SpongebobSquarepantsBattleForBikiniBottom'', if you go outside of the dotted line in any level or the HubWorld and stay there for too long, Hans the Live-Action Hand will come and take your character off the screen, respawning them at the start of the level or the nearest checkpoint, depending on where you were beforehand.
* In ''VideoGame/SonicGenerations'', Modern Sonic can run along the surface of [[VideoGame/SonicHeroes Seaside Hill's]] ocean by boosting, but going too far off the main path will prompt the giant Chopper from [[VideoGame/SonicTheHedgehog1 Green Hill]] to snap him up after a couple seconds.
* ''{{VideoGame/Steambirds}}'' has AA guns with very long range and huge damage that shoot you if you get too close to the edge of the map (though fortunately you can see their firing range).
* Made somewhat ridiculous in ''VideoGame/PokemonXAndY'', where a worker will stop you from going anywhere the first time you visit Lumiose City because of a power outage. However, if you wait long enough, a wandering NPC will walk right past unimpeded.
* The ''Franchise/AssassinsCreed'' series has the Animus acting as the Border Patrol;
-->"Area not available in current memory. Desynchronization imminent."
* ''Videogame/StarControl II'' had the Slylandro Probes. Although they appear throughout the game (as occasional encounters in Hyperspace), if the player leaves the Sol system before helping the starbase, they will literally swarm over the player's ship in an attempt to convince him to [[{{Railroading}} return to Sol]]. It is extremely difficult - but possible - to actually play the game like this anyway. The Border Patrol is removed once the starbase is repaired, though.

----