Spelunky is © 2008, 2009 Derek Yu and Mossmouth, LLC, and is used under the [Spelunky User License v1.1b](https://spelunky.ai/LICENSE.txt). spelunky.ai is an unofficial fan project, not affiliated with or endorsed by Mossmouth. The game and its assets may not be sold. Music by George Buzinkai and Jonathan Perry; sound effects made in SFXR. From Spelunky Classic 1.1, © 2008, 2009 Derek Yu and Mossmouth, LLC. # Boulder From the spelunky.ai wiki: . Verified against the spelunky.ai port [v0.1.10](https://github.com/851-labs/spelunky/releases/tag/v0.1.10) on 27 October 2026. The Boulder is a trap in Spelunky Classic, a great rock that drops from a giant tiki head when the player takes the Mines' Golden Idol, and rolls after him. ![A huge round brown boulder, rolling](https://spelunky.ai/wiki/media/dbb0da14e7366b44/sprites/sBoulderRotateL/anim%404x.png) | Boulder | | | -------- | ------------------------------------------- | | Damage | Crushes the player (every heart)[^1] | | Trigger | Taking the Golden Idol in the Mines[^2] | | Objects | `oBoulder`, `oGiantTikiHead` | | Found in | [The Mines](https://spelunky.ai/wiki/mines) | The Boulder guards [the Mines](https://spelunky.ai/wiki/mines)' [Golden Idol](https://spelunky.ai/wiki/golden-idol). The idol sits on an altar under a giant stone tiki head; 100 steps after the player picks it up, the head opens and drops a boulder two blocks across, which rolls off toward him, smashing through blocks. It kills by crushing: one that lands on the player, or rolls into him, takes every heart. ## How it works **Clip: Boulder.** In the Mines, the player picks up the Golden Idol under a giant tiki head. 100 steps later the head opens and drops a boulder, which lands on him and crushes him, then rolls on to the wall. ([video](https://spelunky.ai/wiki/media/dbb0da14e7366b44/clips/boulder/crush/clip.mp4)) Picking up the idol on a Mines level shakes the screen and sets the nearest giant tiki head going: 100 steps (3.33 seconds) later it opens and drops a boulder from its mouth[^2][^3]. The idol only does this once[^4]. The boulder falls and, the first time it's on the ground and still, sets off toward the side the player is on at 4.5 pixels per step[^5]. It moves twice its speed a step in the open, 8 and 10 pixels on alternate steps at first, because both the game's pass over moving platforms and its own step move it[^6]. On the ground it loses 1% of its speed a step, and stops once it's below 0.5 pixels a step; it turns back at the edges of the level, and edges off a block it's balanced on[^7]. It's kept active wherever it is, rather than only near the screen as most things are[^8]. The clip shows the player standing with the idol under the head: the boulder drops onto him and crushes him, then rolls on to the wall. ## Damage The boulder hurts nothing directly: it's solid, and kills what ends up inside it. A player whose middle is inside it, because it fell or rolled onto him, is crushed, losing every heart, and is counted in the end-of-game statistics' crushed row[^1]. Rolling, it smashes the blocks in its way, as long as it's going at least 1 pixel a step and the block isn't the floor under it, taking any spikes on them too, and loses 0.1 pixels a step of speed for each. An unbreakable block, such as the level's border, or any block once it's slower than 1 pixel a step, turns it back at half its speed instead[^9]. ## Locations Only in [the Mines](https://spelunky.ai/wiki/mines), in the idol room: each side room off the path through the level, except in its bottom row of rooms, has a 1 in 10 chance of being it, once the roll for a Kali altar fails, and a level has one at most[^10]. The room has the giant tiki head near its top and the idol on an altar below it[^11][^12]. The idol does something else in the other areas: in the Jungle the floor around it crumbles, and on a graveyard level the [Ghost](https://spelunky.ai/wiki/ghost) comes; in the Temple it drops the [Ceiling Trap](https://spelunky.ai/wiki/ceiling-trap)[^13]. ## Avoiding - **Leave the room's floor.** The boulder rolls along the ground toward where the player was when it landed. Dropping down a shaft, as in the second clip, or climbing out of its way, lets it roll past; it stops at a wall, or once it has slowed. - **Don't stand under the head.** It drops straight down from the head, onto whoever is still by the altar after 100 steps. - **Bomb it.** A [Bomb](https://spelunky.ai/wiki/bomb)'s blast that reaches the boulder destroys it, leaving rubble and, for each of three pieces, a 1 in 3 chance of a [Rock](https://spelunky.ai/wiki/rock)[^14]. Nothing else breaks it: to the code that destroys blocks, it's unbreakable[^15]. **Clip: Outrunning the boulder.** The player grabs the Golden Idol and drops down a shaft, out of the way of the boulder, which rolls along the corridor above, sets off an arrow trap and stops at the wall; he takes the exit with the idol. ([video](https://spelunky.ai/wiki/media/dbb0da14e7366b44/clips/boulder/outrun/clip.mp4)) ## Interactions - **[Arrow Traps](https://spelunky.ai/wiki/arrow-trap)** fire at a boulder rolling past, as they do at anything that moves in front of them[^16]. In both clips one fires as it goes by. - **Standing on it.** Its top is a platform: a player standing on a rolling boulder is carried along[^17][^18]. ## Trivia - Its step has a commented-out end that would have turned a stopped boulder into a static one, an object the game doesn't have[^19]. - The boulder's destruction of blocks tries to remove their decoration tiles too, but the function it uses never finds a tile in GameMaker 8.0, so the decoration stays behind[^20]. ## FAQ ### How do you escape the boulder in Spelunky Classic? Get out of its way before it lands. It drops 100 steps (3.33 seconds) after the Golden Idol is picked up, rolls toward the side the player is on, and keeps to the floor, so a player who has dropped down a shaft or climbed out of its path is safe. ### Can you destroy the boulder in Spelunky Classic? Yes, with a [Bomb](https://spelunky.ai/wiki/bomb): a blast that reaches it breaks it into rubble, which can leave [Rocks](https://spelunky.ai/wiki/rock). Otherwise it stops on its own once it has slowed down, and stays where it stops. ### What triggers the boulder in Spelunky Classic? Picking up the [Golden Idol](https://spelunky.ai/wiki/golden-idol) in [the Mines](https://spelunky.ai/wiki/mines). The giant tiki head above the idol's altar opens 100 steps later and drops the boulder. ### Does the boulder break blocks? Yes. A rolling boulder smashes through the blocks in its way, and any spikes on them, slowing a little for each; only unbreakable blocks turn it back. ## See also - **Related:** [Golden Idol](https://spelunky.ai/wiki/golden-idol), [Arrow Trap](https://spelunky.ai/wiki/arrow-trap), [Ceiling Trap](https://spelunky.ai/wiki/ceiling-trap) ## References [^1]: `objects/oPlayer1/step.gml:1492-1511` [^2]: `objects/oPlayer1/step.gml:1222-1231` [^3]: `objects/oGiantTikiHead/alarm_0.gml:1-3` [^4]: `objects/oPlayer1/step.gml:1230` [^5]: `objects/oBoulder/step.gml:33-56` [^6]: Quirk 1 (docs/quirks.md) [^7]: `objects/oBoulder/step.gml:11-64` [^8]: `objects/oLevel/step.gml:95-97` [^9]: `objects/oBoulder/collision_oSolid.gml:1-30` [^10]: `scripts/scrRoomGen.gml:86-101` [^11]: `scripts/scrRoomGen.gml:115-116` [^12]: `scripts/scrRoomGen.gml:374-383` [^13]: `objects/oPlayer1/step.gml:1232-1281` [^14]: `objects/oExplosion/collision_oBoulder.gml:1-13` [^15]: `objects/oBoulder/create.gml:9` [^16]: `objects/oArrowTrapTest/collision_oBoulder.gml:1-26` [^17]: `objects/oBoulder/create.gml:11` [^18]: `scripts/gameStepEvent.gml:74-106` [^19]: `objects/oBoulder/step.gml:81-87` [^20]: Quirk 5 (docs/quirks.md) ### Source code - `objects/oBoulder/create.gml` - `objects/oBoulder/step.gml` - `objects/oBoulder/collision_oSolid.gml` - `objects/oGiantTikiHead/alarm_0.gml` - `objects/oPlayer1/step.gml` - `scripts/scrRoomGen.gml` - `scripts/gameStepEvent.gml`