Game Completion: 65-75%, I guess.
Last time I talked about Ar tonelico, I was discussing how the Reyvateil characters, Aurica and Misha, are among the most complicated and deep characters I have ever seen in a videogame. In no small part, this is due to the various game mechanics which let you (or at least, the main hero, Lyner) interact with those two girls.
The first system of the game that helps is the simple conversation mechanic. Often, after going to a new place, using a new spell, or seeing new plot events, a conversation will occur between the hero Lyner and one of the two Reyvateils the next time you rest at camp or at an inn. It is a pretty simple game mechanic, but it is a good way to add a lot of interesting optional conversations to the game outside of the main plot. There are a lot of these (at least 64 for each of the two heroines, I think), which shows off a lot of different things about the characters. Too many games ignore the kind of casual conversation among main characters that would naturally occur, and I think such conversation has a lot to add to any kind of game focusing on character development and interaction, so I am glad to see it here.
Another minor, but fun system of the game are the reactions of the Reyvateils to any item you create through Grathmelding. This is probably the one redeeming feature of the Grathmelding system. Whenever you create an item, the Reyvateil currently in the active party will talk to the main hero about what he just created (often mocking the absurdity of the item combinations, which is is a nice way at poking fun of an odd system), and the go on to propose a name for the new item. These names reflect the sometimes eccentric personalities of the characters (Aurica uses very silly names based on odd logical leaps, while Misha tends to use elaborate and descriptive ones), which is an interesting way to employ interactivity to character development. Also, it is useful, because the main hero often comes up with the worst names for the items he makes, and the second opinion helps.
However, the biggest game system that helps with developing these two characters, and the main game system I wanted to writ about today, is the Cosmosphere system. In order to get more Song Magic abilities for a Reyvateil, you need to enter her Cosmoshpere, a virtual recreation of her mind, and directly observe and interact with her fears, thoughts, and memories in an attempt to help her resolve the scars of her past. The landscape of the Cosmosphere is a reflection of the Reyvateil's mental state, and the people who inhabit it are reflections of how she perceives the people in the real world, rather than how those people actually are. It is a great way to explore the backstory of the characters, see how different characters perceive the world, and show the deeper complexities of a character. With the Cosmosphere system, a single character temporarily becomes the setting, characters, and plot of a whole story.
I am a big fan of subjective dreamworlds, and the Cosmosphere system both fills the tropes of the concept and has a few interesting ideas of its own. Filling out the tropes, there are the prerequisite guides through the mental landscape (the Mind Guardians Hama and Don Leon, who both have humorous interactions with the main hero), the classic idea of diving from conscious thoughts towards the subconscious thoughts, characters based on subconscious ideas that act with surreal logic, and everything that happens is a fantastic analogy for real events, rather than the events themselves. An idea I have not seen before is the way that the landscape of the dreamworld changes slightly every time you reach a new level of consciousness, with old places returning with slight changes and a few new areas appearing each time as the Cosmosphere overview map changes and grows each time, even though the basic layout and certain landmarks stay constant. Another interesting idea is having each level be governed by a particular version of the Reyvateil, each of whom has her own identity both separate from and part of the real-world Reyvateil and the other Cosmosphere versions. Also, there is an interesting severe twist in the tone of the Cosmosphere when you reach the level of the Deep Subconscious. The Expressionist and surrealistic touches are everywhere, especially on the Cosmosphere overview, and they help add to the experience (though sadly these touches are not usually continued into the art for the various areas of the Cosmosphere).
Because the Cosmosphere system exists mostly outside of and separate from the main plot of the game, each Reyvateil's Cosmosphere has its own story based around the idea of helping the Reyvateil heal the wounds of her psyche and mature. These stories are told through conversation (the visuals are simplistic and unsophisticated in the Cosmosphere, which is something of a weakness), and they get very personal and emotional (the voice-acting helps a lot, even if it is a bit uneven in places). On a well-written level of the Cosmosphere, the emotional rewards of helping the heroines heal the scars in their hearts can be vastly greater than the emotional pay-offs from the main story of the game. However, they Cosmosphere system suffers from too many parallels between the stories of the two different Reyvateils (some levels are nearly identical for both sides, with one version of the similar events being great, but the other severely lacking), and some themes are repeated too often in a story, which limits the potential complexity of the story and characters.
While the thematic and narrative elements of the Cosmopshere are great, the actual gameplay of the system is severely lacking. For the most part, you go through the Cosmosphere by selecting an area with a story scene, watching the scene, and then moving on to the next area with scene and repeating the simple process over and over until the level is cleared. There are a number of optional scenes, which is nice, but beyond that there are only minor complications. Success in various events in which the Hero's presence actually matters depends entirely on how many Dive Points you have earned from battles in the main game, and since it is incredibly easy to earn tens of thousands more Dive Points than necessary, there is no real challenge. There are a few places where you get to make a choice, or have a chance at failure, but these are exceedingly rare, with the main penalty of making you simply try again. Adding more interactivity and real gameplay would have helped these sequences a lot.