The PenroseTile example could be improved. There several are bits of code that are not used (which could be very misleading to novice programmers). Also multiple if else statements could be replaced by switch/case block. Here are some of the offending lines. There are also some hacks viz unloading matrix stack, and use of ascii char as int, that are not explained.
Code:

//  float somestep = 0.1;

//  void useRule(String r_) {
//    rule = r_;
//  }
//
//  void useAxiom(String a_) {
//    axiom = a_;
//  }
//
//  void useLength(float l_) {
//    startLength = l_;
//  }
//
//  void useTheta(float t_) {
//    theta = radians(t_);
//  }
 

I would suggest substituting a simpler example, otherwise quite a revision of the original example along the lines of my translation to ruby-processing http://learning-ruby-processing.blogspot.com/2010/05/penrose-tiling-ruby-process....