I love the traditional Celtic designs so popular since Viking days and even pre-Roman. I and others using LB and other languages have worked on computer methods of recreating these. ( search the Forum etc)
The original code I've lost- this is a partial re-invention.
It presents a blank area and the six basic tiles. Some of these can be rotated and reflected. I can't find the original, better drawn master tile image.
Programmatically, it dissects a master image of tiles into the separate tiles, and allows you to select and rotates/reflect them.
Download Celtic Knots as a zip file.