MathPebbles is an interactive website spanning 400 web pages, covering arithmetic, algebra, geometry, functions (single and multi, including calculus of both kinds), probability/statistics, and professional mathematics.
The goal is to have videos and a variety of interactive materials: texts, graphics, programs, proofs, and practice materials. It also will have built-in notetaking.
It is currently under development, but its current version can be found at the test site
This repository is not quite everything you need to recreate this (the external resourcres are not a part of yet nor is there a description), but it contains the content and setup.
It is created using my literate-programming environment.
More words to come.