Gravity Barrier

""Steep Slope Barrier - You would know this was possible if you'd even actually been outside.""

- Comic Book Guy, The Simpsons Game.

As video games become more sophisticated, their environments become bigger and more realistic ... but they still aren't as big as all outdoors. A developer can easily limit an indoor environment -- buildings have walls. Outdoors, however, there's only so many fences a game-developer can put up before every forest looks like some kind of park. A gravity barrier is either a cliff or slope that's too tall to climb... or a drop that kills the player.

Gravity barriers have the potential advantage of looking realistic without being out of place. Sure, the real world has lots of sheer drops or rocky cliff-sides that might be nigh-impassible to the untrained outdoorsman. On the other hand, as graphics have improved, "mountain ranges" that are ridiculously steep yet not much higher than a three-story building randomly jutting out of the mostly-flat grasslands have come to look less like a plausible terrain feature and more like an Acceptable Break From Reality.

The best video-game map-makers can use gravity barriers to restrict player movement, in a way that's not blatant manipulation. A poor game design will use the insurmountable waist height fence -- the obstacle that obviously restricts progress but that anyone could just climb over, given the steely determination of a video game hero. A really bad game design will use the Invisible Wall to prevent a character from progressing further.

Another version of this trope is the water barrier, where a player cannot proceed because a large body of water blocks their progress. Either they will drown if they try to cross it, or the water will continue forever and they will eventually get bored and give up.

Gravity barriers can sometimes be temporary obstacles, until a character comes back with a power-up. For example, the Super Mario Bros. and Wario Land platformers will often have secret items on high platforms unreachable unless the character comes back with the special feather, leaf, or other item that allows them to fly.

The gravity barrier may also be used to allow a player to move forward, but then restrict their backtracking. For example, a character may leap off a small cliff and fall into a new region, and the cliff behind them is unclimbable. The player knows they've both made forward progress and cannot retreat, because they crossed a gravity barrier.

But if a clever player finds a way to get down the cliff without dying, Sequence Breaking may ensue...


 * Sly Cooper levels tend to be bounded by mountains and water.
 * Marathon had numerous gravity barriers, where the player would fall off a ledge and be unable to backtrack. Since the game took place on a space station, these barriers only impeded movement because the artificial gravity was turned on.
 * Half Life 2 has a rooftop chase sequence near the beginning. Even if the player manages to slow their descent, or jump down from ledge to ledge, if their feet touch the ground, they're instantly killed (as if from a fatal fall). The expansion Episode 2 adds lush outdoor environments with mountain vistas and sprawling forests... but the player will often find his progress restrained by unclimbable cliffs that surround the valley he stands in.
 * Left 4 Dead has monsters appearing by climbing over barriers that players simply can't cross... or by leaping from open windows or rooftops that are unreachable from ground level. The implication is that more of the city would be reachable, if the players just had the right tools to climb it. Also, there are city streets visible from building rooftops, but these regions are unreachable because the only way to get to them would be a fatal fall. In the event that a player manages to survive a fall to the street below, but are not supposed to go there, they are incapacitated and then killed within one second. Gravity barriers also block the players from entering some of the monster's spawn points -- infinite zombies "blink" into existence in an unseen, unreachable third-story room, then they jump out an open window to spill into the playing field.
 * However, in "Versus" mode, the players take turns playing as the Special Infected, and they can explore these areas. There's not much to see, and the Infected-only areas are in turn blocked off by walls, sometimes of the invisible variety.
 * Motocross Madness had a Gravity Barrier that can actually be scaled, allowing you to face the second safeguard: the Invisible Cannon.
 * The original Sonic the Hedgehog had gravity barriers. There is a hill in the Marble Zone (part one) that you can run down but cannot run back up.
 * And others that you could only go back up very slowly. So, gravity-impatience barriers.
 * And then the latest games have entire levels SURROUNDED by these, which, due to the inexplicable insistence on extremely linear paths, winds up with long stretches of road over Bottomless Pits. This hasn't been met with much applause.
 * Some racing games (typically of the 'kart'-style) have these as part of the atmosphere, but it also does prevent turning around and driving back. And then there's the ones where the cliff version of the barrier is in effect, where if you leave the track you really leave the track; in Mario Kart Wii, do this on Rainbow Road and you get to watch yourself do a re-entry burn.
 * On that note, the Jet Moto games for the Playstation would often prevent backtracking with huge one-way jumps and large drops off unscalable cliffs. And, of course, half of each game's tracks were loaded with Bottomless Pits.
 * The developers of Elder Scrolls Oblivion attempted this: the many mountains surrounding the land were (mostly) intended to be insurmountable (there are even a few glitched areas that are covered by a perfectly flat ground). Just in case the player does make it to the end of the line, the game pops in with an Invisible Wall for good measure.
 * Several player-created mods remove the invisible walls and make whole provinces like Elsweyr and part of Morrowind reachable, with player-made but roughly in-canon places to visit.
 * The Metroid Prime 3D games used this extensively: either there was an impassable ridge looming high above, insurmountable even by Samus' legendary jumping skills, or a precipice. There was some subtle manipulation as well, in Prime 2: Echoes and Prime 3: Corruption, where attempting to cross a boundary chasm using the Screw Attack would suddenly eliminate the technique's momentum and drop Samus like a stone. Of course, this is absent in the 2D games, where the Wall Jump and the infinite Space Jump allow Samus to leap over any vertical obstacle.
 * The 2D games have their gravity barriers as well, but years of Sequence Breaking have rendered them nearly meaningless. New players who aren't familiar with wall jumping will find plenty of unreachable ledges, often coupled with deep water that kills your mobility upgrades.
 * Metroid Fusion puts a twist on the water variant by making it horizontal as well: until you get the Gravity Suit, you can't use the Sprint Shoes you'll need to escape a flooded area late in the game.
 * Even though in various cutscenes you witness Master Chief surviving jumps and falls from the outer atmosphere... fall 50 feet or so in-game and you're dead. Oddly enough, you die in mid-air rather than on landing.
 * Even worse, many supposedly harmless drops are guarded by instant-kill barriers, usually to prevent players from shortcutting. Notoriously prevalent in Halo 2. For example, on the Arbiter mission "The Oracle", even if you try to shortcut down the shaft by running around the narrow ledges, you will still be foiled by the death barrier (unless you get lucky and somehow avoid it).
 * And then there are the water barriers, where MC suddenly acquires Super Drowning Skills.
 * Somewhat averted in Multiplayer in Halo 2, where super jumping (due to a patch gone right on xbox live) DOESN'T kill the player, even though they may fall in excess of 50 metres. Or how easy it is to get on the outside of the maps and fall off.
 * World of Warcraft used mountains as gravity barriers when it was released. Unfortunately, they underestimated player ingenuity and it was possible to climb over most of them and reach empty lands with unfinished graphics. This was later fixed. It also uses water barriers, in the form of "fatigue" which quickly kills you when you're above sufficiently deep water, regardless of your situation (swimming, walking on water with magic, flying above the water, even as a ghost).
 * You can try to fly from Northrend to Eastern Kingdoms only to discover that it doesn't exist there. The map says that the PC is over Eastern Kingdoms land, but it dies anyway.
 * The expansion made gravity barriers temporary in the new content by adding flying mounts that could be obtained at high levels. This did not apply retroactively to old content, where flying is restricted because the landscape isn't designed for it. There is no Hand Wave.
 * They're adding flying to the original maps in the new expansion. This time providing a Hand Wave: You have to purchase a "flight master's license" - presumably the same one that the griffon/etc handlers already have in order to sell you flights.
 * Averted in Serious Sam The First Encounter with levels placed in the middle of vast, traversable deserts. Some such massive plains have secrets at the far end, if you deign to cross, usually not without a monster encounter mid journey.
 * Crackdown's Pacific City is surrounded by water. Swim too far away from the city - a good distance, surprisingly - and you'll run across an invisible wall.
 * Recent Spider-Man and Incredible Hulk games have featured these, especially the island-city-and-incidentally-your-hero-can't-swim variety.
 * Relatedly, Prototype has the same kind of water barrier. However, while the hero is far too dense to be able to swim, he can jump off the bottom just fine. The game has to artificially force the player to jump in the direction of the shore to prevent him from going out of bounds.
 * And In Famous'', in which the protagonist accidentally electrocutes himself in water more than a couple of inches deep.
 * This is what traps victims in the town of Silent Hill. More specifically, the colossal, bottomless chasms that spontaneously appear and turn the town into a mist-shrouded plateau. And you can fall into the Bottomless Pits in later games.
 * Though this one actually makes a lot of sense. Since Silent Hill is a malevolent, probably-sentient Eldritch Location, of course it'd go out of its way to trap people inside.
 * Fallout 3 uses this on most of the edges of its large map -- nuclear war seems to have kicked up box-shaped range of mountains around Washington DC. If one tries to swim off the south edge through the Potomac, however, you are simply stopped by a pop-up telling you you can't go any further.
 * All the Grand Theft Auto games have water barriers.
 * San Andreas is an exception since there are no barriers to physically hold your character back, although the longer you go away from the mainland, it will take just as long to go back - and realistically, if you just swim off the coast trying to reach the edge you'll run out of energy before long and drown. And if you go into other towns when you are not allowed yet, you get an unshakeable wanted rating, justified by the plot.
 * Red Dead Redemption has insurmountable cliffs surrounding the map.
 * In the Lego Star Wars games the only way of knowing you've encountered one of these, especially when there appears to be a ledge on the other side, is attempting to cross with an astromech droid.
 * The town in all Animal Crossing games has huge cliffs to the west and east of the square town. The second and third games also has a cliff at the north, where the first has a fence. In addition, the first and third games have cliffs across the middle of the town that (along with the river) separate the town into four quadrants.
 * Myst IV has a one age with sheer cliffs. Myst V also has some.
 * In Survivor: The Living Dead, you can't drop from the second floor to the ground as 'Jumping off will snap my skinny legs for sure'. You can throw bombs from the balcony, however, though there was a glitch in some versions that caused them to bounce back up.
 * The Tomb Raider series uses these alot, both to define the outer edges of outdoor levels (unclimbable cliffs) and occasionally to prevent backtracking (slides down really steep slopes).
 * Ironclaw included a Gravity Barrier in a Tabletop RPG. In the middle of the map are the Walls of Calabria: a v-shaped cliff formation leagues long and a mile and a half high. Of course, they're not as much of an obstacle for the flying races, and the second edition reveals that a Noble House of Bats claim the caves riddling it as their domain.
 * Averted by virtue of sheer incompetence in Big Rigs Over the Road Racing where it's entirely possible to drive right over the cliffs surrounding the track and head into the infinite grey void.
 * Borderlands has this in many areas. Falling off a cliff results in instant death, even though you can survive the fall most likely. Jakkob's Cove also kills your character if you try to jump off a cliff to get down to the docks as a shortcut and going too far out in the water also kills you.
 * The Syphon Filter series is somewhat inconsistent with these, a fall heigh that may be harmless in one situation or game will be fatal in another.
 * Alan Wake does this, being set in the mountains of Washington State. There are plenty of areas where gravity barriers stop you from travelling off the beaten path, and yet it works really well. Good level design, thy name is Alan Wake...