Mega Man, known as Rockman (ロックマン Rokkuman?) in Japan, is an action-platform video game developed and published by Capcom for the Nintendo Entertainment System (NES). The first game of the Mega Man franchise and original video game series, it was released on December 17, 1987 in Japan, and localized for North America in December 1987 and Europe in May 1990, respectively. Mega Man was produced by a small team specifically for the home console market, a first for Capcom, who previously focused on arcade titles.

The game begins the struggle of the humanoid robot and player-character Mega Man against the mad scientist Dr. Wily and the six Robot Masters under his control. Mega Man‍ '​s nonlinear gameplay lets the player choose the order in which to complete its initial six stages. Each culminates in a "Robot Master" boss battle that awards the player-character a unique weapon.

Critics praised Mega Man for its overall design, though the game was not a commercial success. Mega Man established many of the gameplay, story, and graphical conventions that define the ensuing sequels, subseries, and spin-offs. It is also known for its high difficulty. The game has since been included in game compilations and rereleased on mobile phones, console emulation services, and PlayStation Portable (PSP).

Extract from Wikipedia.