One thing the OG Game boy is not know for is good shooters. The pathetic non-backlit green and white screen on the original model suffered from horrible blur problems that made things like dodging small objects like bullets nearly impossible for anyone who does not posses Six Million Dollar Man vision. This is one of the reasons after the first few years GB games tended to lean towards simple platformers and puzzle games.
(This has never been a problem for me because I have near-superhuman vision. I am not kidding. Given the right lighting conditions I can see microscopic objects, like dust particles and bacteria. Not making this up. Thing is when I was a kid my vision was even better than it is now, thus the GB screen never game me any problems. For the rest of you humans games like this can be nearly unplayable. Anyway..)
The game is a GB port of the classic NES and Arcade shooter Gradius and comes stock with all the coolness the franchise provides. The ship looks exactly the same and has the exact same powerups, lazers, bombs, and up to two "Options" to increase your firepower. Apparently there was no need to mess with perfection.
The levels are taken straight out of Gradius too, although they are shorter for the most part. Level one is the underground cave with erupting volcanoes, level two has you shooting through bubbles (or glass beads, or rocks, or whatever those things are,) three has you taking down giant Easter Island Moa heads, etc. Level design has not been simplified too much for the small screen and everything flows great. Some of them even have a semblance of parallax scrolling!
Bosses and enemy types are nearly identical to Gradius too, although the bosses are a little smaller. They are a lot easier to beat however.
The concerted effort to reduce the amount of blur with this game is apparent in how the ship moves; It seems to be slightly choppy, however you can tell this was a deliberate decision as all of the enemy types and background moves rather smoothly. When played on a GBC or SP the choppiness of the main ship is hardly noticeable.
All in all a great little shooter, not too difficult (most people should be able to complete it in under an hour or so.) The game does not score any points for originality as seems to be more of a port than a spin-off or sequel. But in terms of pure arcade shooting action the game is top notch and should be a part of any collection.