I'm just beginning to play around with UIElements and I've been struggling with figuring out some basics. The biggest confusion has been how to hook into UI events of various types. Why does the Button element have a "clickable" action? Why do most other elements use "RegisterForEvent<EventType>" to receive callbacks? Is there a method to the madness? Why aren't these consistent? And why isn't the "clickable" event documented in the Events Reference? Why do I have to go to the Button class documentation to find out what "clickable" is?