---
name: "Elevators"
subtitle: "Why the elevator isn't coming, run at 25× until you can see the answer"
date: 2026-08-02
shortlist: true
link: "https://john.fun/elevators"
linkText: "john.fun"
source: "Hacker News — Show HN"
topics: [web-tools, learning-and-reference]
tags: [interactive, algorithms, explainer, free]
description: "An interactive explainer on elevator scheduling — SCAN, LOOK and multi-car dispatch, all running live in the page at up to 25× speed."
---

The SCAN algorithm was patented in 1961: ride to the top, reverse, collect everyone on the way down. LOOK stops at the highest floor actually requested, which is the behaviour you already expect from a lift. Both run live in the page at 1×, 5× or 25×, and a button drops five fresh calls into the shafts so you can watch the assign-it-to-the-nearest-car rule come apart in front of you.