There's a secret message hidden on this site. Find it by building an interpreter for a toy language called "Krul". The description of the language, and what to do with it, can be found here.
Although originally formulated as an assignment for C++ students, you can of course also try to build it in Python, or whatever language you like.
Please note: there are no prizes to win. You also don't need to submit your solution anywhere. It's just for a bit of fun, to challenge yourself with some programming.