We are currently investigating an issue that some people have with the game while running Windows 8.1 and have an integrated Intel HD graphics chip. This doesn't affect all users, only a handful of them. It also doesn't seem to be isolated to our game, as we have seen it affect multiple games on their system.
More information can be found on the post below.
http://steamcommunity.com/app/249950/discussions/0/540736319842473215/