Expounder is a small JS library that implements a concept I had for adaptable experience levels in educational texts. In more concrete terms, expounder allows authors of tutorials to hide their explanations if they expect readers to be familiar with a concept. The author can choose to add a link to the concept, which will appear underlined, and the reader can click on it to expand the next few sentences, paragraph or any other element that explains the concept. This way, people familiar with a term don't need to spend a paragraph reading about it or waste time (and potentially miss other useful information) skimming ahead. You can see an example in the examples directory, on the Expounder page or on one of my posts.