Mega Man made the leap to the original Game Boy in 1991's Mega Man: Dr. Wily's Revenge. Over in Japan the Game Boy Mega Man games were known as Rockman World and some lucky gamer out there managed to snag himself a prototype game pak of the first Rockman World game. What is interesting to me is that extensive collection of Before and After screenshots reveal how Capcom's designers tweaked and redesigned the 2D levels, moving enemies around, reworking platforms, and adding obstacles. Overall it appears that the final version of the game is actually longer and more difficult than the prototype.
[I]t was a bit different from the release version too! I played through the game on my Super Game Boy, and noted differences between it and the release version of Rockman World quite easily. The biggest differences are the layout of many of the levels, the adjusted brightness of some of the graphics, and the music that is slightly different. Oh, and the missing final level of Dr. Wily's stage.
I've always wondered what makes a 2D platformer level "good". How does one know how to balance the number of power-ups with number of enemies? How many small platforms that require careful jumps are enough? How many are too much? Should laser beam hazards deflect Mega Man's shots or not? Should Mega Man enter the boss's room from the left or from above? There is no one correct answer, of course, and looking at these pictures leads me to wonder just how Capcom's designers went about choosing and perfecting these levels.