public override float Evaluate(ISpace space, Point markedPoint, Point unmarkedPoint)
        {
            // walk m_length tiles and verify they are all free
            Point cur = unmarkedPoint;
            for (int i = 0; i < m_length; ++i)
            {
                if (!space.IsAreaFree(cur)) return float.PositiveInfinity;
                cur = DirectionUtils.Move(cur, m_direction);
            }

            // went one too far, so back up to last tile in the dealio
            cur = DirectionUtils.Move(cur, m_direction.Opposite);

            int blockedCount = 0;
            if (!space.IsAreaFree(cur)) blockedCount++;
            if (!space.IsAreaFree(DirectionUtils.Move(cur, m_exitDir.RotationCW))) blockedCount++;
            if (!space.IsAreaFree(DirectionUtils.Move(cur, m_exitDir.RotationCCW))) blockedCount++;
            if (!space.IsAreaFree(DirectionUtils.Move(cur, m_exitDir))) blockedCount++;

            return blockedCount / 4.0f;
        }
        public override float Evaluate(ISpace space, Point markedPoint, Point unmarkedPoint)
        {
            float bestCost = float.PositiveInfinity; // worst possible, best possible is 0

            foreach (Direction dir in m_directions)
            {
                // walk m_length tiles and verify they are all free
                Point cur = unmarkedPoint;
                int counter = 0;
                int blockedCounter = 0;
                for (int i = 0; i < m_length; ++i)
                {
                    if (!space.IsAreaFree(cur))
                    {
                        blockedCounter = Int32.MaxValue - 5;
                        break;
                    }

                    counter += 2;
                    if (!space.IsAreaFree(dir.RotationCW.Move(cur))) blockedCounter++;
                    if (!space.IsAreaFree(dir.RotationCCW.Move(cur))) blockedCounter++;

                    cur = dir.Move(cur);
                }

                counter++;
                if (!space.IsAreaFree(cur)) blockedCounter++; // one past the end

                float score = (float)blockedCounter / counter;

                if (score < bestCost)
                {
                    bestCost = score;
                    m_bestEvaledDirection = dir;
                }
            }

            return bestCost;
        }