Commander Genius aka CloneKeenPlus is an engine which interprets Commander Keen 1-3 (Vorticons Series). As fans and developers we try to implement new features, improve the game play and give the feeling, you are playing the original game.
You need the original DOS game files in order to play on Commander Genius.
Commander Keen: Marooned on Mars and Secret of the Oracle are as shareware already bundled.
Commander Keen: The Earth Explodes and Commander Keen: Keen Must Die! are registered versions which can be purchased from 3D Realms, Apogee, or purchased from someone willing to sell you their copy.