Ever hear of geometrical construction? I learned about it in high school geometry class. It involves using only a straightedge and a compass to draw geometrical figures. Ancient Greeks used it to prove geometrical theorems. I just use it make pretty pictures.
It's a pretty simple process, and makes really cool designs. Always trying to come up with new and cool things to program, I thought I might be able to make a program that could automatically generate similar geometric constructions. But it turns out that even though drawing circles and lines and finding intersections is fairly easy to program, figuring out where circle and lines would look good isn't.
So, I wrote a program to make it easier for me to make geometrical constructions. Instead of having to actually draw things, I could just point and click. The first attempt didn't work very well. It got the basics right (though with some troubling bugs), but the interface wasn't really that good, so it was still more convenient to do it by hand.
A year or so later, I was inspired, and picked it up again. I fixed the bugs, improved the design and added features. Now, it really was more convenient. So I used it. I made a whole bunch of figures to make a coloring book for my niece. Before then, I would on average make less than one a month, but using the program, I made dozens in days.
So, here are some geometrical constructions I've made that look cool.