So Denison (the college I recently graduated from) has a professor who's pretty big into Knot Theory (he's got multiple papers published in the field, and has held the UnKnot Conference at Denison). He had this neat way of representing knots with mosaics. Well, they (he and his students) were using real tiles and everything for this, and so I made a little program to make it so that they didn't have to. I'm going to release it here in case anyone is interested at all about Knot Mosaics and Knot Theory. I know it's a stretch, but, what the hell, might as well.
http://merthsoft.calcg.org/Knot.zip
You could also use this program to design your own Celtic knots, if you're so inclined. Or just mess around, I like doing that.
Oh, and because everyone loves a screen shot, here's a trefoil in a trefoil (this program supports multiple tilesets, this is one I made called "Free Hand", so it's supposed to look like that. There's a more consistent looking one called "Standard"):
http://merthsoft.calcg.org/Knot.zip
You could also use this program to design your own Celtic knots, if you're so inclined. Or just mess around, I like doing that.
Oh, and because everyone loves a screen shot, here's a trefoil in a trefoil (this program supports multiple tilesets, this is one I made called "Free Hand", so it's supposed to look like that. There's a more consistent looking one called "Standard"):