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. # The Shopkeeper's one-step patrol From the spelunky.ai wiki: . Verified against the spelunky.ai port [v0.1.11](https://github.com/851-labs/spelunky/releases/tag/v0.1.11) on 28 October 2026. The Shopkeeper's one-step patrol is a quirk of Spelunky Classic in which a patrolling Shopkeeper's every walk ends on its first step, so he shuffles about. | Quirk | | | --------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Status | GML + Oracle | | Where | [`objects/oShopkeeper/step.gml:283-336`](https://spelunky.ai/wiki/source/objects/oShopkeeper/step#L283-L336) | | Pinned by | `fidelity/replays/enemy-shopkeeper-patrol-one-step.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 patrolling Shopkeeper's walk lasts one step.” | A [Shopkeeper](https://spelunky.ai/wiki/shopkeeper) waiting for a thief is on patrol: he stands, walks a little way, and stands again. The test that ends his walk is the one an Alien turns at a ledge by, without its half that looks for a floor ahead, so out in the open no walk lasts more than a step: he shuffles rather than walks. ## What happens A Shopkeeper on patrol in open ground sets off walking, but his walk's check for a wall ahead sends him back to patrolling on the very next step. He coasts about 10 pixels to a stop, waits, and shuffles again, every second or so[^1]. **Clip: A patrolling Shopkeeper's walk lasts one step.** A Shopkeeper on patrol in open ground sets off walking, but his walk's check for a wall ahead sends him back to patrolling on the very next step. He coasts a few pixels to a stop, waits, and shuffles again, every second or so. ([video](https://spelunky.ai/wiki/media/clips/quirks/shopkeeper-patrol-one-step/clip.mp4)) ## Why On patrol, a Shopkeeper counts down 20 to 50 steps on the ground, then sets off walking a random way[^2]. His walk goes back to patrolling when there's no solid beside his head, a pixel to his left or right: ```gml objects/oShopkeeper/step.gml:309-328 if (facing == LEFT) { if (not collision_point(x-1, y, oSolid, -1, -1)) { status = PATROL; counter = rand(20,50); xVel = 0; } xVel = -1.5; } else { if (not collision_point(x+16, y, oSolid, -1, -1)) { status = PATROL; counter = rand(20,50); xVel = 0; } xVel = 1.5; } ``` [`objects/oShopkeeper/step.gml:309-328`](https://spelunky.ai/wiki/source/objects/oShopkeeper/step#L309-L328), 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)). The same lines in the [Alien](https://spelunky.ai/wiki/alien)'s and the [Mantrap](https://spelunky.ai/wiki/mantrap)'s walks also test the floor in front, `y+16`, where they turn at a ledge[^3][^4]. Without it, in open ground nothing is beside his head, so every walk ends on its first step. That step still sets `xVel` to 1.5 after the test, and his friction takes 0.1 a step off it, so he coasts to a halt over about ten steps[^5][^6]. ## Reproducing it Steal from a shop, or kill a Shopkeeper, and go on to the next level: the Shopkeeper at its exit shuffles in place[^7], and so does a shop's Shopkeeper there, who patrols rather than stands[^8]. The level editor's `!` is a Shopkeeper on patrol[^9], and the replay of the clip's staged scene, on a custom level, puts one in a flat room. In 300 steps he sets off ten times, and every walk lasts one step; after one, his speed is 1.4, and it's gone ten steps later[^10]. A thief's next level shows the same[^11]. ## 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[^6], and the oracle's fingerprint of the replay pins every walk. No option turns it off. ## FAQ ### Why does the Shopkeeper shuffle back and forth at the exit? A [Shopkeeper](https://spelunky.ai/wiki/shopkeeper) on patrol stops walking wherever there's no wall beside his head. The same test in an Alien's walk also needs no floor ahead, so it turns only at a ledge; the Shopkeeper's has no such half, so in open ground every walk ends on its first step, and he coasts about 10 pixels to a halt. ### When does a Shopkeeper patrol? On the levels after a theft, or after the player has killed a Shopkeeper: one waits at the exit, and a shop's Shopkeeper patrols rather than stands. The level editor's Shopkeeper patrols too. ### Do other monsters' walks stop like this? No. The [Alien](https://spelunky.ai/wiki/alien)'s and the [Mantrap](https://spelunky.ai/wiki/mantrap)'s walks have the same test with the floor ahead added, and turn only at a ledge. ## See also - **Related:** [Shopkeeper](https://spelunky.ai/wiki/shopkeeper) ## References [^1]: Clip quirks/shopkeeper-patrol-one-step [^2]: [`objects/oShopkeeper/step.gml:283-298`](https://spelunky.ai/wiki/source/objects/oShopkeeper/step#L283-L298) [^3]: [`objects/oAlien/step.gml:49-58`](https://spelunky.ai/wiki/source/objects/oAlien/step#L49-L58) [^4]: [`objects/oManTrap/step.gml:60-69`](https://spelunky.ai/wiki/source/objects/oManTrap/step#L60-L69) [^5]: [`objects/oShopkeeper/step.gml:531-533`](https://spelunky.ai/wiki/source/objects/oShopkeeper/step#L531-L533) [^6]: Quirk 1 (docs/quirks.md) [^7]: [`scripts/scrInitLevel.gml:245-255`](https://spelunky.ai/wiki/source/scripts/scrInitLevel#L245-L255) [^8]: [`objects/oShopkeeper/step.gml:121-124`](https://spelunky.ai/wiki/source/objects/oShopkeeper/step#L121-L124) [^9]: [`scripts/scrCreateTileObj.gml:151-155`](https://spelunky.ai/wiki/source/scripts/scrCreateTileObj#L151-L155) [^10]: Replay `fidelity/replays/enemy-shopkeeper-patrol-one-step.txt` [^11]: Replay `fidelity/replays/shop-seed-3-thief-next-level.txt` ### Source code - [`objects/oShopkeeper/step.gml`](https://spelunky.ai/wiki/source/objects/oShopkeeper/step) - [`scripts/scrInitLevel.gml`](https://spelunky.ai/wiki/source/scripts/scrInitLevel) - [`scripts/scrCreateTileObj.gml`](https://spelunky.ai/wiki/source/scripts/scrCreateTileObj)