Zool 1

Zool 1 cheat codes: 
To complete this game with ease, type: "goldfish" and hit ENTER.
This activates a cheat mode, whereby if you press 1 you become
invincible for a short while.  2 will skip you to the end of the
level.  3 enables you to skip whole world.

Type "STRETLAMP" at the options screen.(I have a feeling that the
word should actually be "STREETLAMP"!)
Then the following keys give you:
KEYS       EFFECT
~~~~       ~~~~~~
Grey +     Level up
Grey -     Level Down
1          Invulnerability
2          Lose a life (why?!?)
3          ??
4          Restart Level