So I just discovered something cool about the Greenfelt user interface for revealing cards. Maybe you already knew this.
You know how when you hold down (say) 6 the sixes highlight and everything else dims? Well, if you hold down both 6 and R you see just the red sixes; likewise 6 and B for the black ones.
My test for an excellent user interface is this: If I didn't know how to do a thing, and I try the first thing that comes to mind, and it works, then that is one intuitive UI.
@zudensternen I also discovered a while ago that if you hold down both a number and the first letter of a suit, you will see just that card. So if I hold down for example the 6 and a C, it highlights just the 6 of clubs, and so on. (It might have been somebody else on the forum who mentioned this).