// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 13-6: Oscillation
  
  float theta = 0.0;
  
  void setup() {
    size(200,200);
    smooth();
  }
  
  void draw() {
    background(255);
    
    // The output of the sin() function oscillates smoothly between 1 and 1. 
    // By adding 1 we get values between 0 and 2. 
    // By multiplying by 100, we get values between 0 and 200 which can be used as the ellipse's x location.
    float x = (sin(theta) + 1) * width/2; 
    
    // With each cycle, increment theta
    theta += 0.05;
    
    // Draw the ellipse at the value produced by sine
    fill(0);
    stroke(0);
    line(width/2,0,x,height/2);
    ellipse(x,height/2,16,16);
  }