class PenroseSnowflakeLSystem extends LSystem {
  
    String ruleF;
  
    PenroseSnowflakeLSystem() {
      axiom = "F3-F3-F3-F3-F";
      ruleF = "F3-F3-F45-F++F3-F";
      startLength = 450.0;
      theta = radians(18); 
      reset();
    }
  
    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_);
    }
  
    void reset() {
      production = axiom;
      drawLength = startLength;
      generations = 0;
    }
  
    int getAge() {
      return generations;
    }
  
    void render() {
      translate(width, height);
      int repeats = 1;
  
      steps += 3;          
      if (steps > production.length()) {
        steps = production.length();
      }
  
      for (int i = 0; i < steps; i++) {
        char step = production.charAt(i);
        if (step == 'F') {
          for (int j = 0; j < repeats; j++) {
            line(0,0,0, -drawLength);
            translate(0, -drawLength);
          }
          repeats = 1;
        } 
        else if (step == '+') {
          for (int j = 0; j < repeats; j++) {
            rotate(theta);
          }
          repeats = 1;
        } 
        else if (step == '-') {
          for (int j =0; j < repeats; j++) {
            rotate(-theta);
          }
          repeats = 1;
        } 
        else if (step == '[') {
          pushMatrix();
        } 
        else if (step == ']') {
          popMatrix();
        } 
        else if ( (step >= 48) && (step <= 57) ) {
          repeats += step - 48;
        }
      }
    }
  
    String iterate(String prod_, String rule_) {
      String newProduction = "";
      for (int i = 0; i < prod_.length(); i++) {
        char step = production.charAt(i);
        if (step == 'F') {
          newProduction = newProduction + ruleF;
        } 
        else {
          if (step != 'F') {
            newProduction = newProduction + step;
          }
        }
      }
      drawLength = drawLength * 0.4;
      generations++;
      return newProduction;
    }
  
  }