Commander Keen: Invasion of the Vorticons
Episode 1: Marooned on Mars
In Keen 1, the hidden bricks are all in dark areas - look for a gray square in the upper left corner (this tip comes from a Yorp statue as well).
To get to the Secret City in Keen 1, go to the city on the "east" (dark side) of Mars that's about at the planet's Equator. If you go to the dark area at the bottom of that city and head right, you'll find a teleporter. (You have to jump on a hidden brick, over a ledge, then get yourself caught in an ice-launching machine which will propel you over the next wall) This takes you to the hidden city.
Also, if you go to the green city just before the teleporter on the light side of Mars ("left" side, "west" side) and go to the Garg in the yellow tube, and get him to chase you, you can make him "jump" in midair by running left and letting him follow you at his highest speed. It's not really useful but it looks neat :)
If you hit the function keys really fast, it fargles the screen something weird! Walk around... pressing the fire button warps you at random sometimes (and makes another way to "clip" on the Mars map.) Don't do it on a level or you die -- do it on the map. :)
Episode 2: The Earth Explodes
The signs near the Tantalus Rays read "TANTALUS ". If you can't find the Standard Galactic Alphabet, you can translate a lot of the cities. Write down the
symbols, then when you leave the level, see what city you saved and match them up.
(Note that the Vorticons mixed up Moscow and Rome).
When you are standing by the Tantalus Rays in CK2, do NOT pull the switch !! It zaps earth! (The sign over it in the Standard Galactic Alphabet reads "ON").
Episode 3: Keen Must Die
To beat the Mangling machine, you must shoot all 6 space amoebas (spinning purple things) to zap the arms, then shoot the machine's heart. Watch out for the lasers and the meeps! On the floor, you will see 3 bricks that aren't like the others. These are places you can stand and not get crushed by the arms/legs. You must use them all and this requires good timing. Don't try to cross the entire floor without waiting.
Use these wisely. You will miss a lot of fun if you use them all the time!
On the world map press SHIFT-TAB
while walking to bypass a blocking level.
In a level, press C-T-SPACE to get 100 raygun charges, a pogo and all key cards.
Pressing G-O-D will have 3 effects:
You can walk everywhere on the map without being blocked
You are invincible (only bottomless pits can kill you)
While using the pogo, hold CTRL to use the jump cheat.
Note: You must reactivate the GOD mode every time you enter a new level.