God Mode and Full Maps
Pause the game and press 3 + 7, 1 + 9.
To change the screen size, pause the game then hold C and press Left or Right. To center it, pause the game then hold C and press Up or Down.
Secret room: In the test area (reached from the library on level 3), enter the test of magic.
At the red square of carpet with two candles use the levitation spell to see the secret room.