Once the game is loaded and prompts you to press fire, press the
"SPACE BAR" instead.  You will be able to change the speed of the
enemy bullets and other stuff, with the mouse and keyboard.  On the
high score table, type "COMMANDER" on the high score screen (not as
your name) press 'F7' to activate the super weapons 'F1-F6'.  You
should also be invincible.  'F10' turns cheat on/off and 'F8'
advances a level.  On the title screen press 'SPACE' or 'ESC' for
an options menu.