great! your suggession worked. first i enable the guardian and start drawing the guardian larger than the size of the VR playarea. after finished creating all the walls and object cubes, i disabled the guardian back again.
i noticed some games, the floor level fell below the cubes and walls. i couldn't play mini golf at all due to the floor level was too low and my golf stick couldn't reach the ball.
however, castle defender and snake master are working fine.