Kitamura’s initial concept for Mega Man was akin to an “STG” (a “shooting game,” known as bullet hell outside of Japan), with “lots of enemies onscreen at once and you’d have fun blasting them all.” The Famicom’s hardware limitations and the complexity of the programming led the team down a different path. Kitamura envisioned fewer enemies with more varied terrain.
“The number one thing I wanted to do in Mega Man was to make the different weapons interact more with the enemies and the backgrounds,” said Kitamura. “Enemies, special walls, the clouds, the trees…all of them would be alterable by the weapons, sometimes helping, sometimes hindering the player. I wanted the bosses to have different reactions depending on the weapon you used, too. Like if you used a flame weapon and they’re burning, then you freeze them, they actually become super hard and their defense goes way up…but if you use the right powerful weapon on them, then they break apart and you get a brand-new item. Or shooting a boss with a certain weapon could make him get bigger and bigger, or cause him to divide and multiply, or get more HP…there’s so much I wanted to do. Some of those ideas were left in the game, in one form or another. For instance, in [Mega Man 1], if you’re using Rolling Cutter and you get hit by Elec Man’s electric attack, it will bounce off you.”
These concepts would be toyed with throughout the history of the series, yet Kitamura’s other designs, such as the rock-paper-scissors-style weapon and weakness system, would significantly influence the franchise, providing the template for over three decades of Mega Man games.