Board Thread:General Discussion/@comment-26412744-20150518210925/@comment-92.221.100.214-20160702191839

They would need more than jsut player models and animation. They have coded the entire game for singpleplayer. To add in Coop or Multiplayer, they have to re-write and rework the game to fit on a multiplayer infrastructure, and that alone will carry along problems that they were not facing when they made the singleplayer version. It's not "just to add new items and models."