void removeObstacles()
    {
        List <GameObject> obstacles = new List <GameObject>();

        obstacles.AddRange(GameObject.FindGameObjectsWithTag("ObstaclePrefab"));

        for (int i = obstacles.Count - 1; i > 0; i--)
        {
            GameObject obstacle = obstacles[i];
            obstacles.Remove(obstacle);
            Destroy(obstacle);
        }
        l_og.resetObstacles();
    }