In essence: a cut-down version of the first Mega Man game, but with graphics made to fit the monochromatic Game Boy. First published in 1991 by Capcom.
Mega Man actually fits the diminutive Game Boy rather well and the highly challenging (not to mention highly frustrating) gameplay of the Famicom original translates perfectly to Nintendo‘s early handheld.
In this version Mega Man goes up against Cut Man, Ice Man, Elec Man, and Fire Man – all of whom appeared in the original NES game.
Not quite as much fun as the original, or its subsequent sequels, but a decent enough game nonetheless.