On the high score table, enter "SUMITA." for infinite lives.
Load the game and when you get the "insert disk 2 and press space" prompt, press 'HELP' and type "ME", then press the 'up arrow' key. Now insert disk 2 and press space. While playing the game:
'F5' - makes you impervious to collisions
'F6' - makes you impervious to enemy fire
'F7' - infinite credits
'F8' - put the orb in the control of a second player with a stick
plugged in the mouse port