Game will not even launch

[Maize]

Hi! I tried The Long Dark for the first time today, and the game does not even launch. When attempting to launch it from Steam, Steam sets my status to playing the game, and the axe icon appears in my dock. The little dot next to the icon strobes in the fashion it does when an application is launching. This continues for some time (a couple of minutes), and then the icon goes away, and Steam resets my status to not-playing again.

I have successfully verified the local file cache in Steam.

No Unity Player.log file is generated during this process at all, so I'm not sure what further diagnostic information I can provide from that end.

My system is a mid-2011 27" iMac, quad 3.4 Core i7, 12GB RAM, AMD Radeon HD 6970M (2GB). It's fairly stock with the exception of having dual drives -- a 256GB SSD with the OS and applications on it and a 1TB hard disk with my user folder on it -- and having an Apogee Duet audio interface. I'm running Mac OS X El Capitan, version 10.11.2. My steam client is presently a Dec 14 2015 11:22:16 build, Steam API v017, Steam package versions 1450127196.

If you need any further information, please let me know.