Terms of use
Short, and in plain words, because there is no account to close, no payment to dispute and no data of yours for me to lose. What follows is the whole agreement.
Use everything here to learn, at no cost, for as long as you like — at home, at work, in a classroom, in a study group. Solve the exercises, copy the solutions into your own projects, quote a paragraph with a link back. No permission needed for any of that.
Republish the exercises, briefs, hints or solution notes wholesale — as a site, a course, a book or a dataset — or pass them off as your own. They took a long time to write and they are what the site is. Linking to them is always welcome.
This is teaching material written by one person and it will contain mistakes. Nothing here is professional advice, and code you find here is offered as-is: check it before it goes anywhere that matters. If you find an error, the feedback panel is the fastest way to get it fixed.
Whatever you write in the editor is yours and stays in your browser. Equally, running code is your responsibility: the page executes exactly what you type, in your own tab.
Exercises get added, reworded and occasionally retired, and this page can change with them. Anything substantial is recorded in the changelog with a date, so you can see what moved.