void setup()
  {
    size(640, 360);
    background(102);
    smooth();
  }
  
  void draw() 
  {
    // Call the variableEllipse() method and send it the
    // parameters for the current mouse position
    // and the previous mouse position
    variableEllipse(mouseX, mouseY, pmouseX, pmouseY);
  }
  
  // The simple method variableEllipse() was created specifically 
  // for this program. It calculates the speed of the mouse
  // and draws a small ellipse if the mouse is moving slowly
  // and draws a large ellipse if the mouse is moving quickly 
  
  void variableEllipse(int x, int y, int px, int py) 
  {
    float speed = abs(x-px) + abs(y-py);
    stroke(speed);
    ellipse(x, y, speed, speed);
  }