... you can be positive or negative.
(Animation of my photograph by Hazy Dave.)
ADDED: If the image doesn't show up for you — it does for me — it may have something to do with the form HD set the image. I don't know how to change that. Feel free to advise me. I'll put the image below the fold. I think I need to upload a GIF somehow, and I have no idea how to work with that. Maybe this is my cue that I need to learn how to do GIFs myself!
AND: This should work: