A Fantastic Visualization of Prime Numbers and Factors

Without any explanation I can find, here's a stand alone website that spirals numbers on a logarithmic spiral showing factors (and when no factors, primes) for the natural numbers.  (It seems to have problems loading in Firefox, BTW.) It's beautiful in itself -- just simple, elegant, smart -- one of those things words cannot adequately explain -- and a beautiful application of jscript as well. (I checked the evident author -- the "greatgrahmbini" -- interesting YouTube videos -- but....) Via MetaFilter.