Level Cheat:

    * Start a single player game.
    * When on the screen that reads "Start Volcano" type the word bubbles
      (you will hear a sound if you typed it correctly).
    * Type thefullmonty (you will again hear a sound if you typed it
      correctly).  This activates the level selection.
    * Press the down arrow key to highlight Volcano, then press the
      left/right arrow keys to toggle through the levels.

 Other cheat codes:

    * iamzeus = God mode, all weapons, invulnerable, unlimited ammo and
      afterburners. But still there be timers :)
    * lumberjack = This is a fun one, but they hid the effects rather
      well. I stumbled upon it by accident.
      The Scoop: Hit your quick key for Mug. and fire, basic mug. Hit Mug
      again and fire.. you get a spiralling mug. Hit it once more, and
      you get a bouncy-mug. (2 bounces I think) Hit the quick key for
      solaris, basic solaris, hit it again, you get one of those homing
      plasmoids the turrets fire, once more and you get a blue plasmoid.
      (great for taking out lurkers around a corner :)
    * jimbeam = a REALLY fun one like "lumberjack". Select the laser,
      select it again and you get the Levtank electro-version, once more
      and you get the MASSIVELY BITCHING BLOW THE FREAKING HELL OUTTA
      EVERYTHING beam :) Try it, you'll love it.

 NOTE: you will not get all the crystals if you finish the last level.