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