This is stolen straight from the Apogee FAQ in the form it was submitted
to me.  Apologies to all for this one, but this explained it better than
I would ever type.
 
+ Customer Cheat - The backspace key will restore all your energy and give
                   you a death ray, at the cost of all your money.  This
                   will only work in the registered version.
 
+ Debug mode - Set the environment variable "S_HOST" to the value "CASTLE"
               at the DOS prompt by typing "SET S_HOST=CASTLE" (it must be
               in caps).  Then, when you play Raptor, you become completely
               invincible, and have all the weapons at your disposal.
 
[Ed. note: When in god mode, press escape, then press escape again when
           asked to quit and you'll pass the level.]