What I liked: 1. No grand philosophical statements about functional programming paradigm or how awesome is React. (Most tutorials I have seen spend more ink on these than on the real stuff) 2. Easy way to install the tutorial and validate exercises. 3. Using React to teach React (the tutorial is a React program but this aspect is not emphasized).
My suggestions to the Author: 1. Leverage the fact that the tutorial itself is a React program to go one level deeper. This probably would require its own set of pages, each page emphasizing a different aspect such as Router and other components. It took me a while to appreciate that Components are not only for visual elements but they can also change behavior (example: Router). 2. Use HMR to load only the Solution component so that only that part of the page changes when the reader saves his edits. This will be a great showcase of React's power of applying only delta changes to a page. 3. This is a minor nit: the color of numbers in the tutorial is too close to the color of the background. Please use a different color.