Andy, now working primarily with fellow engineer Ryan George on the client side, was confident it wouldn't be that complicated.
“Was implementing Emrakul on Arena difficult?”
“Actually it was super easy, barely an inconvenience”
With a few exceptions all of our ux/interaction code is player agnostic. There were a few somewhat understandable exceptions that were pretty obvious when they came up and weren't too hard to address on on our side of the fence.