The humble beginnings of what we know as an action game can be traced back to the platformer. Mario Brothers and alike trained us in the simple rhythm based, left to right progression model: Start to finish in only one line. Control inputs were limited to simple jump, duck, run, with an additional ‘fire' when earned. While the action game is older and technically matured (3D, polygons, etc.), there is a large contingency of gamers that still craves that simplicity. Mirror's edge is that blend of the new cool with the old fun.
As a human avatar, Faith, your objective is to platform across tops of the buildings, in subways, and through construction yards, using jump, duck, run and the occasional fire buttons when you earn a gun. While having that nostalgic formula, the permutations of controls allows for deep, engaging gameplay.