I don't understand anything about Paul Harrison's Ghost Diagrams, except that the pictures sure are purty, and it has something to do with tiling. In fact, I don't think I undestand any of Paul's blog, except that it involves many things I am interested in, including math, autism, and math and autism. Dense, but fascinating. BTW: It is nothing more than coincidence that this is the day before Halloween and this entry has the word Ghost in it.