They reworked and looked over all the existing content. And added lots of little changes here and there. They redid all the graphics, and added little changes here and there. They looked at all the mechanics, and added little changes here and there. If you don’t think going back into old code and either trying to add new code to it or rewriting it all from scratch in a modern style adds up to as much work as writing it in the first place… I mean there is a very good reason most companies don’t update something unless it was originally made to be updated and we’ll documented, or the original coder(s) are still on hand to dig back in and figure out what creative solutions to problems they had to figure out out how that crazy code even still ended up working… Believe me, it was just as much work as making the game the first time.