// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 16-9: The scribbler
  
  // Two global variables
  float x;
  float y;
  
  void setup() {
    size(320,240);
    smooth();
    background(255);
    // Start x and y in the center
    x = width/2;
    y = height/2;
  }
  
  void draw() {
    // A new x,y location is picked as the current (x,y) plus or minus a random value. 
    // The new location is constrained within the window's pixels.  
    float newx = constrain(x + random(-20,20),0,width);
    float newy = constrain(y + random(-20,20),0,height);
    
    // Draw a line from x,y to the newx,newy
    stroke(0);
    strokeWeight(4);
    line(x,y,newx,newy);
    
    // We save the new location in (x,y) in order to start the process over again.
    x = newx; 
    y = newy;
  }