Darkmode
Robin Flodin playing around with an early darkmode version.
Darkmode or Dark Mode is an option to turn of the global lighting. It was added in the hotfix 1.032, released 14/12/2012. Darkmode can be accessed by setting the Graphics Quality option to High then checking Enable Dark Mode and finally restarting the game.
Secret Beta[]
Before the official release of darkmode there was a test version available for some time, but it was hidden and could only be activated by changing a line in the config file.