A button that's really a sticker - hover and its corner curls back off the layer underneath, press and it pulls a little further.
A button that's really a sticker. Took reference from ozzy.
The peel is one number, how far it's open. Every point of the curl is written as an offset from the right edge and multiplied by that number, so at zero the whole shape is squeezed flat against the edge and at one it's fully out. Two SVG paths are rebuilt from it on every frame: what's left of the top layer, and the underside of the corner that lifted. They share the fold line, which is why the two never drift apart.
A spring drives the number. Hover sets it to one and pressing pulls it a little past that, so the corner gives under your finger. The arrow underneath fades in as it's uncovered, and the lifted corner drops a soft shadow on the layer below.