Yup, pandering to your basest instincts in a way only hi-def video games can
For those who do know what it is and have tried it, you were probably going, "WTF is going on??" This game has one of the least helpful manuals ever.
The greatest resource EVER, and one they desperately should have included as the actual game book, is here at IGN. It's a .PDF document that actually explains everything.
It makes the game much more enjoyable, and shows just how ignorant so many of the "professional" reviewers were. They can keep their 'high-brow', condescending comments to themselves, I fuckin' love a game where you get to play as kick-ass ladies that hack zombies into gooey bits of gore that splatter against the screen, and in heels and a swimsuit at that!