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. # Skulls breaking on any ceiling 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 28 October 2026. Skulls breaking on any ceiling is a quirk of Spelunky Classic in which a Skull thrown up breaks on any ceiling it reaches, where a Jar breaks only rising fast. | Quirk | | | --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Status | GML + Oracle (the ceiling); GML (the wall) | | Where | [`objects/oSkull/step.gml:37-47`](https://spelunky.ai/wiki/source/objects/oSkull/step#L37-L47) | | Pinned by | `fidelity/replays/item-skull-breaks-on-ceiling.txt` | | Row | [docs/quirks.md §1, Bugs and leftovers in the 1.1 source](https://github.com/851-labs/spelunky/blob/main/docs/quirks.md#1-bugs-and-leftovers-in-the-11-source): “A Skull breaks on any ceiling it hits going up.” | The [Skull](https://spelunky.ai/wiki/skull) moves by a copy of the [Jar](https://spelunky.ai/wiki/jar)'s code, with the speeds it breaks at lowered. One of them was lowered past the point of meaning anything: a Skull thrown up breaks on any ceiling it reaches, at any speed, where a Jar has to hit it hard. ## What happens The player throws a Jar up at the ceiling. It arrives slowly and bounces off whole, only breaking when it lands. Then he throws a Skull the same way: it arrives slower still, and shatters against the ceiling[^1]. **Clip: A skull breaks on a gentle ceiling hit.** The player throws a jar up at the ceiling. It arrives slowly and bounces off whole, only breaking when it lands. Then he throws a skull the same way: it arrives slower still, and shatters against the ceiling. ([video](https://spelunky.ai/wiki/media/1d3f433106e37ef1/clips/quirks/skull-breaks-on-ceiling/clip.mp4)) ## Why The Skull's step is the Jar's, copied. Where it hits a ceiling going up, both test how fast it's going: ```gml objects/oSkull/step.gml:37-47 if (colTop and yVel < 0) { if (yVel < 2) destroy = true; yVel = -yVel * 0.8; } if (colLeft or colRight) { if (abs(xVel) > 2) destroy = true; xVel = -xVel * 0.5; } ``` [`objects/oSkull/step.gml:37-47`](https://spelunky.ai/wiki/source/objects/oSkull/step#L37-L47), from `spelunky.gmk`, Spelunky Classic 1.1's source, © 2008, 2009 Derek Yu and Mossmouth, LLC ([Spelunky User License v1.1b](https://spelunky.ai/LICENSE.txt)). `yVel < 0` is moving up, and inside that test `yVel < 2` always holds, so the Skull breaks on every ceiling. The Jar's line is `if (yVel < -3)`: rising faster than 3 pixels a step, as the step has already added its gravity, faster than 3.6 before it[^2]. Against a wall the Skull's threshold is lower as well, 2 pixels a step across where the Jar's is 3, but that one still means something[^3][^4]. ## Reproducing it Throw a Skull straight up under a ceiling it can reach: it breaks there, however slowly it arrives. The replay of the clip's staged scene, on a custom level, throws a Jar up under a ceiling four blocks up; it reaches it rising at 3 pixels a step and bounces off, breaking only when it lands. A Skull thrown the same way reaches it at 2.4 and breaks there[^5]. The wall's lower threshold is read in the code, and not yet checked against the original game. ## In the port The spelunky.ai port reproduces it exactly: it's in docs/quirks.md's list of the 1.1 source's bugs[^4], and the oracle's fingerprint of the replay pins both throws. No option turns it off. ## FAQ ### Why does the Skull break on the ceiling in Spelunky Classic? Its code tests for a speed below 2 pixels a step downward while it's moving up, which always holds. So a [Skull](https://spelunky.ai/wiki/skull) breaks on any ceiling it reaches, however slowly. ### Does a Jar break on the ceiling? Only rising fast: a [Jar](https://spelunky.ai/wiki/jar) breaks on a ceiling it hits going up faster than 3 pixels a step, and bounces off whole otherwise. ### Does a Skull break against walls more easily too? Yes: a Skull thrown faster than 2 pixels a step across breaks on a wall, where a Jar needs more than 3. That's a lower threshold, not a broken one, so a slow Skull still bounces off. ## See also - **Related:** [Skull](https://spelunky.ai/wiki/skull), [Jar](https://spelunky.ai/wiki/jar), [Throwing](https://spelunky.ai/wiki/throwing) ## References [^1]: Clip quirks/skull-breaks-on-ceiling [^2]: [`objects/oJar/step.gml:37-41`](https://spelunky.ai/wiki/source/objects/oJar/step#L37-L41) [^3]: [`objects/oJar/step.gml:43-47`](https://spelunky.ai/wiki/source/objects/oJar/step#L43-L47) [^4]: Quirk 1 (docs/quirks.md) [^5]: Replay `fidelity/replays/item-skull-breaks-on-ceiling.txt` ### Source code - [`objects/oSkull/step.gml`](https://spelunky.ai/wiki/source/objects/oSkull/step) - [`objects/oJar/step.gml`](https://spelunky.ai/wiki/source/objects/oJar/step)