Collectible Card Game Headquarters

I am a long time lurker and have been thinking about trying my hand at creating a 3d playing field to make things a little more user friendly for users more familiar with the wotc games. Is the game logic heavily embedded into the GUI or is there somewhat of a separation?

Just trying to get some sort of idea on how to start pulling the game logic out.

Game and Gui are seperated.
That alows different Gui ports like for Desktop and Mobile.
The game only calls the Gui for stuff like: "choose card"
The Gui itself should not call the game, and if not very often.