What's up with the grade ranking?, And how the hell do i get a good one? Options

[Crushinator]

What exactly determines how high your grade is at the end of a fight? The highest I've been able to achieve so far is B+, and that was on a battle I didn't feel went too well. On some battles where I take NO damage at all, and don't lose any cards, I only pull a C or C+, even if I totally decimate the opponent.

Is there some secret "style" guage in the game that rewards using good combos or something, or is it based on the types of cards you use (strong ones, or weak ones???). It doesn't make any goddamn sense. And how the hell am I supposed to get better cards when you can only get a good score using good cards (WHICH I DON"T HAVE!!!)???

[kyori]

Here's what PSOW thinks it is, looks about right too. (Hehe, and I just had an A+ with Saligun on Guardian 3, man I love her)

35 + (Attack Damage - Damage Taken) + (Max Card Combo x 3) - (Story Character Damage x 1.8) - (Turns x 2.7) + (Action Card Negated Damage x 0.8)

The number that results is checked against this chart
Score Rank
0-14 E
15-24 D
25-29 D+
30-39 C
40-49 C+
50-59 B
60-64 B+
65-74 A
75-84 A+
85+ S