This is an editor for H's, T's, and (rich) graphs.
Opening index.html with a web browser starts the application.
Some utilities for processing the save files can be found in utils.py.
A relatively up-to-date version is hosted at https://apps.adamv.be/HEdit/ (an example).
Please refer to https://adamv.be/Edges-to-edges for a brief introduction of H's and T's.