I have a recursive substitution-rule to tile the plane, which seems simple enough but nevertheless does not seem to be discussed in the normal places (like the tilings encyclopedia, http://tilings.math.uni-bielefeld.de/substitution_rules). Google searches haven't helped either (example: an Image search with the keywords: tiling regular pentagon triangle). The rules for my tiling can be seen here: http://mrob.com/pub/math/images/penta-tiling.jpg I consider this a "simple" and "obvious" tiling because there are only two rules, and each rule tries to maximize the size of the pentagon(s) on the right-hand side. However, it is "non-simple" in the sense that, with repeated applications of the substitution rules, increasingly many different sizes of triangles and pentagons are produced. - Robert -- Robert Munafo -- mrob.com