DOS

Commander Keen 1: Marooned on Mars

Go to the Dark Side of the Mars, once you are there, go to the gray mars base in the centre of Mars. Enter it. Play the level normally. Once you reached the red keycard, you have jumped over a chasm with fire. That's the way to the secret base. Jump down, but avoid the flames on the bottom, which are direct beneath the route you fall. If you survived, take the right way, there is a big wall. You can't jump high enough, even with the pogo, to cross it. But you can see a spot on the wall of the chasm, there you must go with the pogo. Now jump over the wall, but be careful not to fall into the freezing machine. If so, you will be frozen and than land in the fire and die. Jump over the fire, stand directly left of the wall, jump with the pogo directly into the freezing ball on the point of the cannons maximal fire distance. If you do it correct, you will be catapulted over the wall. Once you landed, use the ray of the robot to thaw yourself, now you are ready to jump into the teleporter. When you done this, you are back on Mars' worldmap, far east beyond the mountain east of the gray base you started. Now you can play the secret base...

This base you must enter

This chasm you must fall down

Avoid the fire, and jump to the point where Billy is

This is the idea behind it, but it was not timed enough

Thaw yourself and jump into the teleporter

Welcome to the secret base...