private void CreateBomb(Direction dir)
    {
        Vector3 offset;

        switch (dir)
        {
        case Direction.UP:
            offset = Vector2.up;
            break;

        case Direction.DOWN:
            offset = Vector2.down;
            break;

        case Direction.RIGHT:
            offset = Vector2.right;
            break;

        case Direction.LEFT:
            offset = Vector2.left;
            break;

        default:
            offset = new Vector3(0, 0, 0);
            break;
        }
        LitBomb bomb;

        bomb = Instantiate(bombPrefab, transform.position + offset, Quaternion.identity).GetComponent <LitBomb>();
        sm.AddBomb(bomb);
    }