Another cool algorithm animation site: http://rosulek.github.io/vamonos/demos/ uses Vamonos (http://rosulek.github.io/vamonos/). However, it looks like you have to write the algorithm twice, once in pseudocode to present to the reader and once in javascript to execute. In the Javascript code, you annotate the execution with the corresponding lines in the pseudocode so that the library can show what's executing.

I haven't dug into Vamono to figure out how that interacts with the browser's event loop. Duncan's use of ES6 generators for that interaction is clever, as is Will's Tailspin JS interpreter.

Wow, that is super sweet. I have been planning to add user interaction to algomation.com but have not had the time yet. The input mechanism would need to support validation and defaults so that algorithms could always run unattended but otherwise very doable despite the web workers that I use on the site.