Programmaticaly generating a Croatian interlace pattern
The Croatian interlace, known as pleter in Croatian, is a three-ribbon decorative pattern almost uniquely found on old Croatian stonework from the times of the duchy and later kingdom of Croatia (9th — 12th century), such as stone inscriptions and church decorations11 The most famous ones are the Baška tablet found on the island of Krk and the baptismal font of Prince Višeslav.
So for someone who loves history, math and programming, generating it programmatically sounds like an interesting challenge.