While playing, type 'TOGETHER IN ELECTRIC DREAMS'.  Then, try the 
following:

< - Go down a level 
> - Go up a level 
G - More Missiles 
T - Less Missiles 
N - Extra Lives 
 
Fly to the top of the screeen to avoid missiles.  Slow down on levels 
8 and 17 to avoid rocks.  Go full speed to dodge infra-red missiles.