anchor.diff:    }
   
     // Detect if we're outside the playing board.
  -  bool isOnCanvas(Coord coord) {
  -    return (coord.x >= 0 && coord.y >= 0 && coord.x <= width && coord.y <=
  -        height);
  +  bool isInsidePen(Coord coord) {
  +    return pen.isInside(coord);
     }
   
   
  
positive.code:   int getY() {
      return y;
    }
  }
  
  class Snake {
    int maxSize = 3;
    List<Coord> coords = new List();
  
    int width;
    int height;
  
    int points = 5;
  
  
negative.code: 
    Snake(int w, int h) {
  
      pen = new Coord(w,h);
  
      coords.add(newRandomCoord());
      assert(coords.length == 1);
  