Holy moly. I had my suspicions Magic would be a good candidate for something like CLIPS when it comes to software implementation. Do you have a source for that info? What an amazing bug.
The source for them using CLIPS is a conversation I had with Arena team lead Ian Adams in a Magic-community Discord.
The source for the bug is a video WotC did that I can't find right now that featured the Arena team talking about developing Kaldheim - the bug came from the card Alrund, God of the Cosmos.
> So first, a quick summary of how the rules engine works. When a game of Magic is in progress on MTG Arena, the program that is tracking the state of the game and enforcing all the rules-correct card interactions is called the Game Rules Engine (GRE). It's one of the two main programs that we work on. It's written in a combination of C++ and a language called CLIPS, which is a variant of LISP.
The source for the bug is a video WotC did that I can't find right now that featured the Arena team talking about developing Kaldheim - the bug came from the card Alrund, God of the Cosmos.