(BETTER VERSION AVAILABLE- I have a more compact and less resource intensive version available now. This one is still very much usable and has a cool spiral-like opening and closing sequence, it just has more requirements.)

I've made a 2x2 piston "floor-door," as I like to call it, which opens and closes from within the floor. I've uploaded a video detailing it and showing how to build it. I'm posting it here to get it and myself some attention. :3

Give credit when it's due; I built this design entirely myself through trial and error.

Thanks!