// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 14-17: Nested push and pop
  
  // Global angle for rotation
  float theta = 0;
  
  void setup() {
    size(200, 200);
    smooth();
  }
  
  void draw() {
    background(255);
    stroke(0);
    
    // Translate to center of window
    translate(width/2,height/2);
    
    // Loop from 0 to 360 degrees (2*PI radians)
    for(float i = 0; i < TWO_PI; i += 0.2) {
      
      // Push, rotate and draw a line!
      // The transformation state is saved at the beginning of each cycle through the for loop and restored at the end. 
      // Try commenting out these lines to see the difference!
      pushMatrix(); 
      rotate(theta + i);
      line(0,0,100,0);
      
      // Loop from 0 to 360 degrees (2*PI radians)
      for(float j = 0; j < TWO_PI; j += 0.5) {
        // Push, translate, rotate and draw a line!
        pushMatrix();
        translate(100,0);
        rotate(-theta-j);
        line(0,0,50,0);
        // We're done with the inside loop, pop!
        popMatrix();
      }
      
      // We're done with the outside loop, pop!
      popMatrix();
    }
    endShape();
    
    // Increment theta
    theta += 0.01;
  }