The initial jump to the Game Boy was a rocky one, showing a mixed bag of good ideas and sloppy handling of the new format. This one is often criticized for its short length and difficulty, and there were enough strongly designed rooms to show that the designers had the potential to do better.
The first set of stages showed that the Game Boy's limitations could be worked around, but also included a fair bit of lazy design. Cut Man's stage showed a variety of good enemy configurations that work on the smaller screen, but the unnecessarily upgraded Big Eye was at its worst here. Ice Man's was competent overall, but Elec Man's had its share of filler for every good thing it did, and Fire Man felt as though the designer had checked out.
Only a handful of enemies were bought in from Mega Man 2, and even fewer were used well, with Scworm having by far the best placement. Much of the game is designed more like an alternate Mega Man 1 than an even mix of 1 and 2.
Most of the problems caused by the smaller screen reveal themselves in the enemies brought over from the Nintendo Entertainment System series. We have less room to react to Big Eyes, Sniper Joes, and offscreen Gabyoalls. Bunby Heli is much less of a threat when we can often reach it with the buster as it appears. Changkey Maker's projectiles and Pipi's broken eggs take up much more of our available screen space, making them much tougher to avoid.
Cutting Wheel and Super Cutter worked well as new enemies, with both remaining still at first so we don't have to dodge something flying at us from a few feet away. The change to Metall is interesting in this context. Screwdriver shows that there is still enough space available to dodge through the old angles, so Metall's spread may have been tightened just to give it a more unique behavior.
It's unfortunate that we didn't see more new enemies, appropriate alterations to old enemies, or simply better choices from the other games.
The final stages showed a few good ideas, particularly the active Joe fights and the mad dash through Wheel and Cutter, but too much of their space was taken up by easy enemy encounters, Mole tunnels, and the vanishing block segments. For having only two stages, and using only four previously, these should have been full of new enemies and surprises. Unfortunately, the reasons we didn't get more out of them are likely the same as why we got only two in the first place.
Still, this gave us Carry, and while its use was pushed a little too hard in the first stage and sloppily implemented in the second, the item itself is amazing. It is really unfortunate that it was ignored after this, as the ability to save yourself from a pit with a quick weapon switch provides so much utility without the game having to go out of its way to give you reasons to use it.
The first round of weapons gives us just the right amount of power for how tough the stronger enemies can be. The second group had potential, but we just didn't have enough game left to get much out of them beyond Bubble Lead's damage upgrade and Atomic Fire's strength against Dr. Wily. Atomic Fire really needed to hit harder against large enemies, and the Quick Boomerang was at best an alternative to the Rolling Cutter if you ran out of it.
As for the bosses, most were made much more difficult by the smaller rooms, both from their size when moving around, and the reduced area to dodge projectiles in. The attempts to weaken Ice Man and Fire Man swung a bit too far in the other direction. Elec Man, Flash Man, and Bubble Man made it through the transition best, but overall, these bosses just weren't meant to work in this environment, and Enker didn't turn out any better.
However, Wily himself had a good showing. His first form attacks fast but is manageable by standing next to him, while the second half requires a more careful approach. I'd call this one of the things this game did best, had Enker's weapon not been so easy to run out of over a couple attempts.
Overall, there was a lot of potential here wasted by mistakes that could have been fixed with a little more thought and effort. The game is acceptable, in the sense that I've seen much worse transitions of NES games to the Game Boy, and the designers clearly showed that they could make good encounters on it, but the recycled enemies and bosses could have used a few more changes to fit the screen size.
With only six stages, each room should have been given more attention, and Fire Man's stage, the double Mole tunnels, and double vanishing block hallways at the end showed that this didn't happen. Its good qualities were promising though, and leave me excited to see what the rest of the series managed to do.