Recursive Drawing
Whether you like this or feel like it's not as powerful as you'd like, try <a href="http://recursivedrawing.com/" rel="nofollow">http://recursivedrawing.com/</a> in a similar vein with discussion here: <a href="https://news.ycombinator.com/item?id=3951255" rel="nofollow">https://news.ycombinator.com/item?id=3951255</a>. It's simultaneously simpler and more expressive than this tool in my opinion.