I still find somewhat remarkable the complexity in a simple button on the web. These are just 6 common states that may each have their own appearance and behaviour.

Common button states

You can see this trend in most technology products. Increasing subtleties and functions are added improving what a product can do. At some point, the complexity is sufficient to force us to focus efforts on simplification (or the benefit great enough that a simpler technology will take over) - while maintaining functionality. Classic menus migrating to context-sensitive menus; the original NES controller, to the xbox controller to Wii and Kinect control, Yahoo’s list-the-web, to Google’s search the web, multiple glasses to photochromic glasses, and so on.

I believe this observation is from Edward De Bono, but I learned it from Darrell Mann. I keep finding it helpful.

Things get more complex before they get simple

They are apparently there to help you see the keys to make it easier to type. If you can type already, fold them away — it’s better for your wrists to have no bend.

Fold away keyboard feet