Game Completion: Hard to say... 30-50% complete, I imagine.
As I said before, Ar Tonelico is a quirky RPG. It has a unique setting, unusual mechanics, and a very interesting battle system. I talked a lot about the Grathmelding system over the last week, so I think I will just focus on the game's battle system for today. It is fairly complex, though, so I think I will just try to dissect it piece by piece.
Reyvateils: The central focus of Ar Tonelico is its cast of girls known as Reyvateils, and the battle system is no different. Unlike pretty much every other RPG I have played, where characters are mostly differentiated by stats and abilities, Ar Tonelico makes Reyvateils completely different than other characters. They are controlled differently, are the only characters to have MP, they can't use normal attacks, they use different kinds of equipment, only one can be in the party at a time... Most importantly, they are the single most important member of the team, with every non-Reyvateil character being a glorified meat-shield in comparison. This is even taken into account in the plot, with every strong group of enemies or NPCs having a Reyvateil or two in the team. I think this kind of total separation to be a really interesting idea that could be really useful in a lot more games, and it used to great effect in this game.
Song Magic: Reyvateils are important in battle because they use Song Magic. The song magic system is very different from typical RPG special ability systems, since it is based on MP being a restriction of power and duration, rather than being a simple limitation of how often a spell can be used. The MP cost of a spell is constantly counted down in small iterations of time between character actions, so that a Reyvateils MP reserve, which can easily be thousands of MP, can be completely drained by a single spell with a cost in the range of 30-70 MP. What is more, it is not a simple system of spells taking a while to cast; it is a system where you can freely control the chanting time, and as such the duration (for support-type Blue Magic) or power level (for attack-type Red Magic) of songs. You can cast a quick and cheap attack spell to do a light hit, or take a lot of time to build up a powerful attack spell that will defeat every opponent at once. Also, whenever you are not chanting a spell, the Reyvateil's MP quickly regenerates, so MP is not something that has to be conserved (though MP restoration items do have uses, and there are limits to how often you can use many songs).
The system is very fluid and fun, and the different powerful spells open up a lot of different strategies for the game (work towards a single finishing blow, work to resist damage, activate healing so that you can freely use the attack skills of the frontline fighters, etc), and it is very easy to switch strategy in the middle of a battle. This is easily one of the most innovative and fun systems I have seen in a game in quite a while.
The Ambience Field: This is the point where the glorified meat-shields come back into the game. As a whole, non-Reyvateil characters have three important functions: protecting the Reyvateil (a minor system, but a good one), another one I will describe below, and empowering the Ambience Field through their regular attacks. Essentially, each time a character attacks an enemy with a weapon, that enemy's Ambience Field value will rise (to a max of three), and that number will fall at other times. The higher the Ambience Field, the stronger the attack of a Reyvateil's Red Magic will be. It is a system which rewards a dedicated attack strategy and good timing with very powerful Red Magic attacks. It reinforces the central importance of the Reyvateil in battle (and thus in the story). It is both minor enough to not be necessary in minor battles, and powerful enough to be invaluable in boss battles, and I like it a lot.
The Harmogauge: The other important thing that non-Reyvateil characters do in Ar Tonelico is boost the all-important Harmogauge. It is a meter which is filled from the left with a blue line (based on the actions of the normal characters) and from the right by a purple line (based on the actions of the Reyvateil). When the two lines connect, a Harmocrystal is filled and the gauge resets (though it can be emptied to the point that a Harmocrystal is lost). Filling Harmocrystals has enormous benefits: the chanting speed of Song Magic increases, the power of normal characters increases and they gain access to stronger Skill attacks, powerful counterattack moves become available, and enemies will drop more items at the end of battle. That last benefit is very important.
It is necessary to get a high Harmoguage level in almost every battle, simply because it is the only way to get enough items for grathmelding and for sale (since selling dropped items is one of the few ways of getting sufficient amounts of money). This turns every random battle into a struggle to build the Harmogauge as high as possible before the enemies die. While that might sound like a chore, I find it is a rather good way to make normal battles more interesting, so they don't become an exercise in just dispatching enemies without any thought or excitement. However, it has a drawback...
The problem with the Harmogauge system is that an element of it, the Limit Gauge which controls your maximum number of Harmocrystals, is a highly flawed system, because the only efficient way to build that gauge to its maximum is to fire two reasonably charged shots of Red Magic, and it takes far too long to fill the gauge with Blue Magic. As a result, trying to get the rarer item drops of weak enemies (who won't survive two shots of red magic) is incredibly difficult, and the game rewards the offensive playstyle of using Red Magic a lot more than Blue Magic, despite their parity in longer boss fights. The game would probably be a bit better if the Limit Gauge system was altered somewhat.
As a whole the battle system of this game is a lot of fun. The only real drawback is that this game is not terribly difficult, so it seems that it is never really necessary or even possible to use the system to its full extent. This is certainly a battle system that should be used as inspiration for game mechanics of the future.