The Polyglot Code Tools are tools I've been building slowly over the past few years, for visualising and understanding software built in a wide range of programming languages (hence "polyglot").
The best place to start is the Overview
These docs are published to https://polyglot.korny.info
Source code for this site is at https://github.com/kornysietsma/polyglot-tools-docs
The site is built with The Rocketseat Gatsby theme for documentation websites