Parkour Brothers

Perhaps you have heard the warning: playing Mirror's Edge will make you vomit. Now that's a video game!

The new game is a sort of a "first-person runner": You're a courier who travels across the rooftops of a locked-down, police-state city, delivering black-market messages by using acrobatic feats of parkour. You're constantly leaping over gaps 40 stories in the air, tightrope-walking along suspended pipes and vaulting up walls like a ninja. Or a Nike commerical.

What makes Mirror's Edge so different? It's the first game to hack your proprioception.

That's a fancy word for your body's sense of its own physicality — its "map" of itself. Proprioception is how you know where your various body parts are — and what they're doing — even when you're not looking at them. It's why you can pass a baseball from one hand to another behind your back or how you can climb stairs without looking down at your feet. Most first-person shooters do not create any sense of proprioception. You may be looking out the eyes of your character, but you don't have a good sense of the dimensions of the rest of your virtual body — the size and stride of your legs, the radius of your arms. At most, you can see your arms carrying your rifle out in front of you. But otherwise, the designers treat your body as if it were just a big, refrigerator-size box.

Mirror's Edge, in contrast, does something very subtle, but very radical. It lets you see other parts of your body in motion. When you run, you see your hands pumping up and down in front of you. When you jump, your feet briefly jut up into eyeshot — precisely as they do when you're vaulting over a hurdle in real life. And when you tuck down into a somersault, you're looking at your thighs as the world spins around you. What's more, the game world feels tactile and graspable. And because the game is designed around the concept of parkour, or moving through obstacles, most times when you see something that looks like you could jump on it, you can. And the gameplay requires it.

The upshot is that these small, subtle visual cues have one big and potent side effect: they trigger your sense of proprioception. It's why you feel so much more "inside" the avatar here than in any other first-person game. And it explains why Mirror's Edge is so curiously likely to produce motion sickness. The game is not merely graphically realistic; it's neurologically realistic.