This is an instance of the CS Circles site originally created by the Centre for Education in Mathematics and Computing of the University of Waterloo, Canada.
CS Circles depends on a multitude of free software, including Linux, Python, WordPress, CodeMirror, Polylang, and FlexiGrid. Our sandbox is a customized version of Mooshak safeexec. Thanks to Philip Guo and Peter Wentworth for building the original visualizer and its Python 3 port. The banner is by Ben Sutherland, modified and distributed according to the CC-BY 
license.
This website is open-source, thanks to a SIGCSE Special Projects grant! The course materials are available under a Creative Commons license. See the git repository or the authoring page for details.
You can read about the site's design and philosophy in this paper from SIGCSE 2013.
The text and code for this site were written by David Pritchard and Graeme Kemkes, with administrative help from Andy Kong. We thank Brian B., Gord C., Tor M., and Douglas S. for help getting started, and we thank Cora B., Lisa R., Francis C., J-P. P., Peter B., Jack T., Steve S., Kyle B. for valuable feedback.
We are deeply grateful to the following people who helped translate the site: Brice Canvel, André Roberge, Serge Bays, Nico Westbury, Ashlyn Osborne (French), Wolfgang Pohl, Marcel Inhoff from BWINF (German), Ries Kock, Joost Rijnveld (Dutch), Jurgis Pralgauskis (Lithuanian), Kevin Wang, Harris Chen, Selena Yang (Chinese), and Marzanna Miąsko (Polish).
The error message hints were produced through a project of Ayomikun (George) Okeowo at Princeton University.
This project is run by the Centre for Education in Mathematics and Computing at the University of Waterloo, which has been funded in part by the Bill & Melinda Gates Foundation. We also thank GitHub for freely hosting our git repositories.
Lastly, thanks to everyone who has used the site and especially those whose feedback has helped improve it!
