Build a polytope. Count its points. Repair a polynomial. Check the proof.
Open the Chapter 1 laboratory · Every exploration is open: change an example, compare cases, and jump anywhere with the map.
Five chapters follow the paper from pattern-avoiding permutations to what is and is not proved. Every exploration is open: jump anywhere, and come back to anything you skip. Marks only record visits; they do not grade anything. The first steps of Chapter 1 live in the laboratory page.
This investigation needs JavaScript and must be served over HTTP (for example python -m http.server).
python -m http.server
