Well there's two things: -A UI can't/can't-not adhere to Fitt's Law; Fitt's law tells you where to put things to make them easy to hit* it says nothing about w

Well there's two things: -A UI can't/can't-not adhere to Fitt's Law; Fitt's law tells you where to put things to make them easy to hit* it says nothing about what you should put there. -The entire edge is infinite but if your mouse has any horizontal velocity (which is extremely common now with wide screen monitors) a top menu item is only as deep as it is long. It's still easier for being 2D but it isn't infinite. *more accurately it's a mathematical model that tells you how long it takes to acquire a target with a mouse. I have no actual proof that speedy = easy.