If you've played Crysis 3 on the PC, you've probably noticed that the first level, even on a powerful system, chugs. Badly. It gets you off on the wrong foot with the game, because you start worrying more about hardware than the experience, and that sucks.
Stick with it, though; bizarrely, as the first level's tight corridors open up into vast expanses of a ruined New York, Crysis 3 runs a lot smoother. Which doesn't make sense, seeing as it should be the other way around.
This weird scenario has a weird solution, though: it's all to do with ropes. Yup. Ropes.