anchor.diff:  }
   
   class GreedyStrategy extends EvaluateStrategy {
  -  const GreedyStrategy(int searchDepth): super("greedy $searchDepth", searchDepth);
  +  const GreedyStrategy(int searchDepth) : super("greedy $searchDepth", searchDepth);
   }
   
   class AntiGreedyStrategy extends EvaluateStrategy {
  -  const AntiGreedyStrategy(int searchDepth): super("anti greedy $searchDepth", searchDepth);
  +  const AntiGreedyStrategy(int searchDepth) : super("anti greedy $searchDepth", searchDepth);
   
     num evaluate(Board board, List<String> moves) {
       return -board.score;
  
positive.code: class RandomStrategy extends Strategy {
    static final Random _random = new Random();
  
    const RandomStrategy(): super("random");
  
    String nextDirection(Board board) {
      return Board.DIRECTIONS[_random.nextInt(Board.DIRECTIONS.length)];
  
negative.code: }
  
  class GreedyDownStrategy extends EvaluateStrategy {
    const GreedyDownStrategy(int searchDepth) : super("greedy $searchDepth down", searchDepth);
  
    num evaluate(Board board, List<String> moves) {
      return moves[0] == "up" ? -1 : board.score;
  