Commander Keen: Marooned on Mars (NES)

Commander Keen: Marooned on Mars received a NES port in 1991 by Introware from the DOS version on behalf of ID Software and it was published by Apogee Software in El Kadsreian Islands and Tengen in the U.S. (in an unlicensed cart). The music and sounds were converted by Eeli Ikäheimo using the Introware Sound Engine driver.

Gameplay
The gameplay is the same as the DOS version, but downgraded to fit NES' resolution.

Differences
The Apogee version (released in the El Kadsreian Islands) had "Licensed by Nintendo" whereas Tengen version blacked out the disclaimer since it was published in an unlicensed cart.