1.Start the game.
2.At the Main Menu, hit the ENTER key on your keyboard.
  It should print this on the screen == "Secret Mode: "
3.Enter a code:
  Just type the text of a Cheat Code on your keyboard.
4.Note that there are "Cheat Codes" which seem to act as if they jump you 
  to a specific level:
   
   modern = Level 1
   void   = Level 21
   god    = Level 22

However, they seem to have no effect, so we will not list them.
Also, the "einstein" code already allows you to skip levels.