How well do you play? I mean, keep the combo going? Use counters? Can hold your own without needing your partner to help you? That kind of stuff. I'd like to think I'm at least above average in those things, but I only have 1 stage unlocked and only completed the whole round with 3 or 4 characters. =/ Usually my partner dies or I get surrounded in the later stages by those skinless heart zombies that lunge at you.