Holographic Card Shader
Hover the card and it leans with your cursor while the foil catches the light, the way a holo card flashes when you rock it under a lamp.
The finishes are a WebGL fragment shader on the card face. The tilt angle stands in for the viewing angle, so the shine sweeps against the card rather than with it, and head-on the card looks almost plain, just like the real thing.
On Prism, the portrait is printed over the foil so the rainbow engraving only hits the background, a trick borrowed from real holo cards.