LONGPLAY: Commander Keen Episode 2: The Earth Explodes (1990) [MS-DOS]
Channel: Dosgamert
Date: 19/10/2014

In Commander Keen 2: The Earth Explodes, Keen has assembled his ship in Mars and returned home, only to find the Vorticon Mothership hovering over the Earth, ready to destroy all of Earth's cities and wonders! Keen must sneak aboard, stop the imminent destruction of Earth and find a way to neutralize the Mothership. If he fails, the Earth will explode.
In the middle of the night, while his parents think he is asleep, Keen returns to his backyard clubhouse his Bean-with-Bacon Megarocket still cooling down from his recent Martian excursion. He flies to the Vorticon Mothership, sneaks aboard and docks his ship at the weakest area, the Bottom Galley. With incredible luck, Keen finds a nearly empty Vorticon HyperPistol, the weapon of the Vorticon Elite.

The Vorticons onboard are controlled by the Grand Intellect, a mysterious being on their homeworld of Vorticon VI. There are eight X-14 Tantalus rays in the Mothersip, each pointing to a specific city on Earth. Keen has to find each of the rays and disable them.
Keen is equipped with a blueprint of the Vorticon Mothership he "borrowed" from one of the Vorticons he dealt with on Mars. He uses this to navigate his way around the ship. It is used as the map level, and is notable for being printed by ACME.