Page "Commander Keen" Paragraph 36

The player can find ray guns for firing projectiles bolts left or right to kill enemies.

Some enemies die after one shot, some after multiple shots, and others are impervious to the ray gun.

If Keen touches an enemy or a hazard, he immediately loses a life.

Enemies include fictional Martian species Yorps and Gargs ( in episode 1, after which a yorp follows Keen onto his ship, the Bean with Bacon MegaRocket, only to be noticed by Keen when he lands back on Earth, at which point he makes it his pet and calles it Spot ), and Vorticon or Vorticon-related creatures ( in all three episodes ).

Throughout the games the player can collect colored keycards to open doors with corresponding colors and bonus items in the form of sugary foods and sodas / colas ( Those can be jumped on for a boost before being collected ).

For every 20, 000 points, the player is awarded another life.