Castlevania: The Adventure for Game Boy is a barebones Castlevania game that plays it safe, to a fault.
It seems that the Game Boy's technical limitations prevented Konami from retaining some key elements in the series on the handheld, some of which you'll notice right away and some as you progress though just the game. Firstly, you lack the use of special weapons like the axe, dagger, holy water, etc, which are present in previous iterations. This issue isn't too significant considering the game is so stripped down that it can be completed without the special weapons. It is because Castlevania: The Adventure is missing many of the design elements of the games before it, is why it’s familiar but different. The levels are still traveled horizontally and vertically in both directions, respectively, and you still have more or less the same skill set from the previous games in the series. Other than than missing some of the weapons and items from the series, Castlevania: The Adventure does a good job of providing challenge in both the levels and combat. You'll make your way from the outer entrance of Dracula's castle into the castle to face the Prince of Darkness himself; all the while avoiding giant rolling eyeballs, spikes, bats and bosses before facing Count Dracula.
One of the first things I became aware of was how slowly your character moves. I understand that this pace is probably a deliberate counter-measure to the screen blur that many faster paced Game Boy games suffer from, however, there are platformers on the system with more things going on visually that still provide a faster pace than this, with tolerable blurring. To its credit, Castlevania games have never been known for their fast paced gameplay anyway. Though trudging through the levels at this pace can get frustrating, especially since some of the areas in the levels require you to be nearly perfect on the controller to pass them, particularly the moving spike level, which is also a bit too long a sequence.
Another gameplay aspect is the platforming, especially jumping some of the wider gaps. You have to be pixel-perfect on the jumps or die, and though the controls are good, the game is pretty unforgiving, usually starting you back a few screens from where you left off, but even if you run out of lives, you can continue indefinitely. You’ll more than likely notice the absence of the doors and stairs in this game, which seem to have been replaced by ropes. The change works for this game and lends itself well to providing much of the challenge in avoiding the spike level's section where you have to be nimble on the ropes to prevent being crushed by the ever-moving wall of pointy death. The ropes and level design also make it fairly easy to find the secret areas in the game if you're looking for them since there isn't a lot of ground to cover, which leaves the options of finding the hidden entrances pretty straightforward.
Some fans of the series may have issue with the fact that though your whip can be upgraded to extend and shoot fireballs, it can also be reduced to the level one cowboy belt you start off with if you take damage, with each hit reducing the upgrades by one. It is very frustrating to be fighting using a long-rang strategy with the fireball upgrade, only to lose it to one of the cheap hits by the enemies in the game. Other gameplay elements like hearts are still in the game, but unlike their traditional use, they now serve as health-ups, and 1Ups are still few and far between, but you probably won’t need them since you can continue ad infinitum. Most of the enemies you'll face can be dealt with in one hit, but there are some that will require a more thorough lashing to defeat; this is truer for the bosses, which are also pretty well balanced.
Lashing your whip is just as familiar as any Castlevania should be, with the sound it makes nearly identical to the previous titles. The whip animation - though minimal - shows the over handed style that the Belmont family trademarked since the beginning. The grayscale visuals are decent, looking very clean and surprisingly bright, but the backgrounds are not the most detailed. There is also minimal animation for enemies and even the star of the show. However, the graphics are pretty well done considering the limited power of the GB.
The music in the game is surprisingly good considering the inherently poor audio facilities of the handheld. The levels feature very memorable tracks that I actually did not grow tired of hearing. Though, I don't recognize the music from any of the previous games, they still sound relatively familiar with accompanying sound effects to pronounce the action. Eyeballs exploding, bats shrieking, and a few other sounds effects round out the presentation side. It's pretty amazing what Konami accomplished with four channels of sound.
I believe that Konami attempted to give GB players a portable Castlevania experience that is meant to be pick up and play gaming in short sessions. I think this is the reason for the length of the game and the barebones approach to the gameplay. System limitations of the Game Boy gave way to much of the lack of aesthetic presentation, but I still think that more could have been done to make the game better and more polished. Overall, Castlevania: The Adventure is mediocre addition regardless of if it was meant to be pick up and play, and of the few redeeming qualities it does have, the only one I can recommend is that it is a Castlevania game and from the perspective of a fan of the series, I suppose if you’re someone who wants to play every game in the series, you just might enjoy this entry in the long-running series.