// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 13-5: Polar to Cartesian
  
  // Polar coordinates (r, theta) are converted to Cartesian (x,y) 
  // for use in the ellipse() function.
  float r = 75; 
  float theta = 0;
  
  void setup() {
    size(200,200);
    background(255);
    smooth();
  }
  
  void draw() {
    
    // Polar to Cartesian conversion
    float x = r * cos(theta);
    float y = r * sin(theta);
    
    // Draw an ellipse at x,y
    noStroke();
    fill(0);
    ellipse(x + width/2, y + height/2, 16, 16); // Adjust for center of window
    
    // Increment the angle
    theta += 0.01;
  }