Movement question

[ThreepE0]

Just a quick question: I noticed there's no way to rotate the camera; I can move my mouse in a circle a bunch of times in order to rotate which direction is up (not sure why this works, but I've seen it happen in some games too,) but there doesn't seem to be a key to do that. I noticed there's a gimbal locked setting in the demo, but no keys bound to rotate. Would this be easy enough to implement?