comments, considering 8 buttons, changed HIGH/LOW

I have swapped the HIGH and LOW in lines 73 and 75 so it registers presses when you first push the button rather than on release. I don't think that will break it.

Other than that I've just added comments.

How on earth are we gonna iterate over the pins? I want to use a map or hash or something. Even if we had an array of pin numbers, it's no good, as the pins aren't next to each other :P