Tiling is softwear mixing celtic knots and (some) of the 17 wallpaper groups used in midle east art.
Tiling create images by placing "strings" on a "fundemental zone" of the plane (which depend on the choosen wallpaper group). This zone is replicated to fill the plane. In the process the strings are knoted following celtic knots rules.
Each wallpaper group has its own fundemental zone which is delimited either by pair of identified borders and/or by miror-like border.