anchor.diff:      points += delta;
     }
   
  -  void showData() {
  -    showPoints();
  -    showDirection();
  -  }
  +
   
     void showPoints() {
       var pts = querySelector("#points");
  
positive.code:   int maxSize = 3;
    List<Coord> coords = new List();
  
    int cwidth;
    int cheight;
  
  
negative.code:     }
  
      // If we're not at max length, then grow length
      if (coords.length == maxSize) {
        coords.removeAt(0);
      }
      coords.add(newHead);
  
      assert(coords.length >= oldLength);
  