Press ~ after starting the game, at the screen where the items are
described. Proceed for two more screens and press [Backspace] at 
the screen with the magic lamp to enable cheat mode. 
Then, press one of the following keys during game play.

Result                  Key
---------------------------------------
Level select          - 1A through 1M
Level skip            - [Keypad plus]
Five apples           - A
Five gems             - G
Toggle invincibility  - H
Toggle free movement  - M
Toggle objects        - U
100% damage           - [Tab]