Following Symphony of the Night's success on the Playstation (despite Sony's attempts to bury it), there was naturally more demand for the "metroidvania" format. Circle of the Moon was actually a launch title for Nintendo's new Game Boy Advance system, all but ensuring it an audience, and the fact that it sold over 1 million copies naturally ensured the franchise would find a home on portable machines for years to come. Circle of the Moon follows the same open-ended roaming as the original, with occasional boss fights and earning new items that allow reaching new areas. Rather than having an extensive equipment and spell system and a shop like SotN, though, Circle of the Moon has something called the "Dual Setup System" (DSS), which allows you to combine two cards together to create a new effect. Cards depicting the Greek gods form the base effect while monster cards provide a modifier; for example, Mercury adds elemental damage to your weapon; combining it with Salamander causes fire damage, Serpent causes ice, and so forth. A lot of these effects are very niche and situational while others are almost comically overpowered - for instance, there's little point to using elemental effects to target specific enemies when you can just attach a flat 25% damage boost to all of your attacks. Similarly, summoning orbiting fireballs that inflict continuous contact damage lets you quickly destroy many bosses, much faster than would be possible just using your whip and/or subweapon. Unfortunately most cards are a very low drop chance from various enemies, so you'll have to do a lot of tedious farming to collect them all. The high difficulty of many boss fights also ensures you'll really want specific card setups to stand much of a chance, unless you really like naked experience grinding too. Being limited to only one effect at a time is also a bit annoying, particularly as SotN allowed you to freely mix-and-match weapon types, armors, spells and boost effects while here they're all tied to random drops and/or the DSS. Two of the strongest cards are also tied to rare drops from postgame bosses at the tail end of a long gauntlet of boss fights, so you'll be doing an arduous amount of grinding if you want to get full completion.
Circle of the Moon is far from perfect, but is a passable first attempt at a portable Castlevania. Despite the obvious downsizing it retains a good semblance of the open-ended roaming and character building that made SotN fun, and it's got plenty of moody atmosphere, story twists and the same rewarding gameplay loop that made the format a hit to begin with. Worth checking out, especially since you can get it for a pittance with the Castlevania Advance Collection on multiple platforms nowadays.
