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