Commander Keen Episode Two: The Earth Explode is the second episode in Invasion of the Vorticons trilogy.
In Episode Two, Keen returns to Earth only to find the Vorticon mothership hovering above with its deadly X-14 Tantalus Ray cannons locked on to eight of Earth's greatest landmarks: the Big Ben (London), the Sphinx (Cairo), the Sydney Opera House (Sydney), the Statue of Liberty (New York), the Eiffel Tower (Paris), the Colosseum (Rome), St Basil's Cathedral (Moscow), and the White House (Washington D.C.).
Keen has to find and deactivate each of the cannons to save Earth. Unlike the first game which had a happy and friendly atmosphere, almost everything in this game is hostile towards Keen, from the floating machine gun robots to the electrified floors.
There are some improvements to the game engine in Episode Two too. Most noticeable improvements are light switches and moving platform.
You can download Commander Keen Episode Two: The Earth Explodes here.