AWESOME

 
 To become indestructible and to get infinite money and fuel, complete
 the first attack level. When the shields/weapons screen appears, move
 the cursor to the top left of the screen and place it in the shields
 box. Hold down the [+] key on the keypad and press fire.
 The screen will flash indicating that the cheat has been activated.
 Now during play pressing [F1] disables the enemies, [F6] replenishes
 lost energy and keys [1] to [0] give you the various weapons.


If you're still confused by the trading sections, then here is a way of
easily getting to the end of the game.  Simply go to the outer-most planet
and you will be presented with another animation in the same style as the
intro.