A common form of obstacle in video games, usually in mountainous areas, are boulders, balls of snow or even mook attacks coming from off screen, that pester the Player Character until they are close enough to the source, at which point the obstacle simply disappears without explanation. Usually at least two of the following conditions are in play:
- The obstacle activates on coincidence. It is never a constant obstacle that happens as a natural part of the environment. If the boulders are going to fall, you have to just happen to be in the way.
- You cannot see why the obstacle happens. Is someone tossing the boulders down? Are natural forces at work during this? Is there a reason why this only happens when you're in the way? You can never find out the exact cause.
- It stops as soon as you get close enough. Whatever the cause, as long as you're close enough to the source (but not out of range or sight), it will cease to attack. Think removing enemies by bringing them off-screen, only inverted.
The name derives from guerrilla warfare, referring to how the obstacle tends to attack in set amounts before retreating or stopping altogether.
Related to Stalactite Spite.
- The Legend of Zelda has a few of these:
- The Legend of Zelda has boulders tumble down if you walk by the river at the very northern part of the world map. They only stop when you leave the area and you never get to see where they are coming from.
- A Link to the Past: While Link is going to the Tower of Hera, boulders will fall down on him when he crosses a certain area on Death Mountain. These boulders fall until Link reaches the summit, which, despite the boulders clearly coming from there, becomes barren of all activity.
- Ocarina of Time: While Link is going up Death Mountain, the volcano erupts boulders onto him when he enters the road in front of it. Getting to the wall means that the volcanic activity stops.
- Breath of the Wild: In addition to Link-seeking magma bombs in a few areas of Death Mountain (triggered by a giant mechanical lizard), boulders will often tumble down ravines while Link is trying to climb them; the same happens with giant snowballs in cold areas. In many cases, there are enemies nearby who could conceivably be responsible, but in others there are no living things nearby.
- During a few levels of Super Mario Bros. 3, there is water along the bottom of the level, and when you pass through a certain region, the water level starts to rise and fall, then stop again at a certain point. Also, Bowser's Castle has some horizontally traveling jets of flame that come from nowhere.
- In Super Mario World, Bullet Bills spawn in certain places at the edge of the screen, without a cannon to shoot them out.
- Super Mario RPG has Booster Hill, where an endless number of barrels roll down. As the whole thing is a mini-game, they don't hurt Mario, but they do cause him to stumble back.
- In Super Mario 64, in Bob-omb Battlefield, you travel up a spiral mountain which giant boulders constantly roll down. When you reach the top of the mountain, you see that the boulders were coming out of the side of it... but not with any explanation or way to stop it.
- In Mario Kart 64, going offroad in D.K.'s Jungle Parkway will result in the driver having coconuts thrown at them until getting back on the main road.
- System Shock 2 features a room with a cyborg ninja and a wave of never-ending metal crates falling down in it. The crates fell down on you, which only mysteriously stopped once you actually killed the ninja.
- Happens on some levels in Crystal Caves, always helpfully featuring a sign saying "Falling Rocks." They stop falling if you are near the top of the level.
- In the last part (before the Final Boss) of the last level The Smurfs on SNES and Genesis, various things are tumbling down the stairs you're climbing. While this could be the Big Bad's doing, he has no reason not to simply wait for you, especially considering his tactics and placement in the Boss Battle.
- Guerilla boulders are an occasional obstacle in Dynasty Warriors, Samurai Warriors, and Warriors Orochi. Squads of Mooks are generally stationed in the area where the rocks apparently come from, but nobody is seen actually chucking them. (In at least one case, however, the rocks are magically conjured.)
- Joe & Mac deluges players with boulders falling from somewhere offscreen.
- Holy Diver has a level where boulders spawn continually at either edge of the screen for no apparent reason.
- Downland had some rooms where an endless series of bouncing boulders would come from an unmarked spot near the side of the screen.
- Tomb Raider always has boulders or similar objects that are sitting on a hill or hidden alcove that will only start to roll down the moment you pass by them. There are also boulders that don't move at all unless you trigger an Event Flag.
- In Jak II: Renegade, there's a section where you have to climb up a cliff with these as obstacles: getting hit will likely send you down a fair bit of the cliff. While the Mountain Temple level it's in isn't that tricky overall, the unpredictability of these boulders turns this one section into That One Level all on its own.
- A common obstacle in Adventure Island games are boulders that come crashing down at you from atop any peak you travel towards.
- An Untitled Story features the Highlands, a small area that features no dangers except for a constant avalanche of boulders falling from a nearby mountain. When you're on said mountain, these boulders are nowhere to be seen, which is a good thing since there are many other dangers instead.
- Jungle Hunt: The third stage of every round has these, which the jungle man must jump over or duck under.