Interactivity in webpages is usually limited to simple link clicking and working with form elements, however, let your imagination run off with the idea of ‘reactive documents’.

A reactive document, in the context of the web, is a document which enables the reader to play with values, premises and assumptions, and see instant feedback in the same document. Wolfram Alpha is famous for doing some of this.

Bret Victor (check his site out, it’s great) explains the concept best in his essay Explorable Explanations, and he has released a Javascript library to create these reactive documents. It’s called Tangle.

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