Any mirror in the mansion (except for the large one that reflects the invisible ghosts) can be used to warp back to the entrance hall. Set the Game Boy Horror to first person mode and press A to examine the mirror. This allows you to save the game conveniently. In the first room of the mansion there is a mirror under a cloth. Vacuum the cloth off, then go into first person mode with the Game Boy Horror. Search the mirror and the screen will go blue. Nothing really happens, yet the world twists upside down.