Description:

Mega Man 4 (stylized as Mega Man IV) is a 1991 platform game developed and published by Capcom for the Nintendo Entertainment System. It is the fourth installment of the original Mega Man series and was originally released in Japan on December 6, 1991. The game was released in North America the following January, and in Europe in August 1993 by Nintendo. The game's story takes place after the third defeat and supposed death of Dr. Wily in Mega Man 3, and features the Earth coming under threat from the mysterious Russian scientist Dr. Cossack and his eight "Robot Masters". Fearing the worst, Dr. Light sends Mega Man to save the world once again. Mega Man 4 carries on the same action and platforming gameplay as the first three games, in which the player completes a series of stages in any order and adds the weapon of each stage's boss to Mega Man's arsenal.

Source: https://en.wikipedia.org/wiki/Mega_Man_4