Possibly the worst actual "Metroid"vania there is.

Most of my issues with this title stem from character being a bit too floaty and slow. There is no other 2D Castlevania - classic or Metroid-style - where controls feel as bad.

The level design is effectively non-existent. If you were to tell me to picture a room from a Dracula's Castle from any Castlevania game, I can do so. Ever since NES those games made sure to feel like actual spaces. Not this one. Rooms are big empty spaces with some plafroms thrown for good measure which makes every area save for the sewer feel the same.

The sewer is only different because there's water, you see.

This is a hard game that doesn't really reward grinding. Other 'Vanias happily give you various weird items to play with, but with the exception of DSS cards which only select few monsters carry you'd be lucky to find an equipment item that barely raises your stat.

DSS system isn't really that fun and feels like a prototype for later Souls system. It requires 2 cards to activate, effects can be unappealing, fairly boring or even unclear.

It's not a bad game and maybe worth playing once, but I'd pick any other Castlevania to replay before this one. Frankly, even some that are objectively worse simply because they offer more variety.

Probably the best of the GBA's launch lineup, and the first Metroid-style Castlevania to be released since Symphony of the Night which was very welcome for this series after a few years of experimental 3D games that failed to really hit the mark. Circle of the Moon is pretty challenging and memorable, but considering the game's dark and detailed visuals it must have really sucked to play it on the launch model GBA's notoriously-dark screen, and its level design and scope were eventually usurped by the other excellent Castlevania games on GBA and eventually DS.

Always a risk playing older games with modern eyes. I enjoyed my first step in to the world of Castlevania with Circle of the Moon. The DSS card system is just great, really fun and unique. Fantastic atmosphere and music. Hunting for new equipment and cards is very fun and addicting. The game is not without its faults though. No auto run and limited shortcuts make map traversal become tedious. Summoning button combos are cumbersome, and also make later bosses quite trivial. Many items are rare drops from specific enemies, requiring a guide if you want to try out everything.

Castlevania: Circle of the Moon was released as a Game Boy Advance launch title. And developer Konami Computer Entertainment Kobe’s swan song, for the subsidiary was dissolved the following year. The game kicks off with the protagonist Nathan and his partners walking in on Camilla’s revival of Dracula. Their attempt to interrupt ends with mentor Morris being held as sacrifice as Nathan and Morris’ son, Hugh, plummet down a long shaft to the castle’s underground. The two rivals split up and the player takes control of the whip-wielding Nathan, who leisurely strolls and whips his way past bomb-throwing skeletons fire-spitting bone heads. That is, until you locate the Dash Boots, so Nathan can finally start exploring in earnest.

Circle of the Moon aims to balance traditional Castlevania with Metroidvania-inspired exploration. In addition to your traditional sub-weapons it introduces the Dual Set-up System (DSS). Combining two cards, dropped by enemies, results in a magic enhancement. Sadly, it’s poorly implemented. It relies heavily on RNG with low drop-rates and no hints as to which enemy could potentially drop what card. I finished with only half the cards but also with 23 Leather Armors, which served no purpose as there’s no means to exchange redundant items for money or, say, cards. The game also ramps up its difficulty fast in the second half of the game, mostly by throwing hordes of evolved (recoloured) enemies at you. Boss fights aren’t exactly the cherry on each area’s cake, either. Half of them float around, sparsely animated, firing off projectiles while you dodge and facepalm for losing the Cross sub-weapon yet again.

Conclusion: Circle of the Moon offers a solid but uninspired Castlevania experience. Some unfortunate choices in its design leaves a lot of potential untapped and it might’ve been a great entry in the series with a little more budget (and perhaps love) from Konami’s headquarters.

While this game isn't worthless, I could write a full essay on why it sucks so much.
It has the worst enemy design out of all the metroidvanias in this series by a lot, awful screen crunch, shitty controls, and its general idea of game design makes it feel like it was made by people who don't play video games.
It can occasionally be fun, but its design philosophy is just inherently flawed in essence.
The soundtrack is very good, though I dearly wish there were more original songs because the few that there are are fantastic.

A pretty brilliant game. It is the first attempt to boil down Symphony of the Night's new direction for the series into handheld, but the limitations that come with that mean they still kept one foot in the old Castlevania design direction. It's very much a compromised work, a bastard child of both veins of Castlevania, but to me it's the best of both worlds.

Of course, Iga would take later GBA games and make them look and feel exactly like SotN did on PS1, but the simplistic design of CotM makes it stand out as its own thing entirely (not to mention it helps visual clarity). Movement of different and takes some getting used to, like the old games you hop vertically more than leap horizontally. There are fewer secrets to discover and the game uses a basic "card" system for upgrades and builds. It's all very much in the experimentation mode.

But there are some really cool bosses that we will see reused later (giant ball of corpses, anyone?) and the card system is ripe for exploiting. And what is a Castlevania game if not to cheese to the maximum extent of your ability? This game is prime cheese, in every interpretation of that statement.