Bottomless Pits, this mountain isn't so bad. Except now they're being pelted with boulders! It's a weak avalanche that they can tell is coming from higher up the mountain. Something has to be causing all these boulders to fall down on them. After a short detour up the mountain, they were expecting to find the source of the boulders. It'd only make sense for there to be a reason for this avalanche, right? Nope! Upon locating what would've been the source of the boulders falling down, the hero not only finds themselves without an answer as to why rocks rained on them, but now the boulders have simply stopped. Enter Guerrilla Boulders, a form of obstacle in video games. Commonly being boulders, balls of snow, or even mook attacks coming from off screen, these obstacles ruthlessly attack the playable character until the player is 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 Legend of Zelda has a few of these:
- 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, a volcano erupts boulders onto him when he specifically stands on the road in front of it. Getting to the wall means that the volcanic activity stops. This even happens after Link rids the Gorons of their problem in Dodongo Cavern.
- 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.