Roller Coaster Chess

A while ago I drew a comic about playing chess on a roller coaster. Various xkcd readers took up the challenge. Pictured above: Andrew Burke, Chris Ranker, Ryan DowlingSoka, and Chance Brown. To see more pictures of chess on rides, go to If you think you can do better, go for it, and send […]

Perl Appetizers

You may have noticed that the knapsack problem in today’s comic has two solutions. I thought that (spoiler alert!) the 1, 0, 0, 2, 0, 1 solution was the only one, but 7, 0, 0, 0, 0, 0 — seven orders of mixed fruit — also works. Why did this happen? Well, I checked my […]