Invincibility, full maps:
Pause game play and press 3 + 7, 1 + 9.

Adjust screen centering:
Pause game play and press C + Up or C + Down.

Adjust screen height:
Pause game play and press C + Left or C + Right.

Hidden room:
Locate the test area from the library on level 3. Enter the test of magic and locate the red carpet section with two candles. Cast Levitate to see a hidden room.