Multi-threaded Towers of Hanoi with Air Traffic Control

Live site: https://jconning.github.io/multithreaded-towers-of-hanoi/

The classic recursive Towers of Hanoi, where every ring flies on its own thread. Several rings can be airborne at once, and an air traffic controller keeps them from colliding mid-air: a ring flies right up to the edge of the airspace still owned by the ring ahead of it and holds there until it clears.

Background

Jim Conning submitted Multi-threaded Towers of Hanoi with Air Traffic Control as an entry into the Java Contest of 1995, which commemorated the launch of Java 1.0. It was a Java applet that ran in the browser, with each ring flying on its own Thread. It stopped working when Java 1.1 blocked Thread.sleep() for security reasons, and the source code was lost. This is a re-creation, designed and implemented by Claude Opus 5.5 on October 26, 2026.

Stack

• Plain HTML, CSS and JavaScript. No framework, no build step, no dependencies.
• HTML5 Canvas for rendering.
• One Web Worker (a real OS thread) per ring flight, coordinated by an air traffic controller on the main thread through message passing.

The page itself explains the algorithm and the air traffic control rules in detail.

Running locally

Open index.html in a browser. No server needed.

License

© 2026 Jim Conning. Released under the MIT License.