With so many things for an interaction designer to think about, it’s easy to forget about good ol’ Fitts’ Law!
What’s Fitts’ Law, you ask?
In a nutshell, it states that the time to acquire a target is a function of the distance to and size of the target. The shorter the distance and the bigger the target, the shorter the time it takes to, say, click on it.
For more information, check out this great (and fun) introduction to Fitts’ law, written by prolific software designer, Bruce Tognazzini.