An internet connection is required to play a free trial of the game in order to allow us to distribute the trials for free.
The connection allows us to use our strong DRM which basically ensures that although we have sent you the whole game for free, you will have to pay to unlock it once your trial has ended. Without that protection most publishers wouldn't allow us to send the whole game out for free!
We also use the internet connection to be able to assess whether or not your PC will be able to run the game, so that we can warn you before you spend time downloading a game that is too demanding for your PC.
Finally, we use it to provide in-game hints and tips, as well as letting you enter competitions and give us feedback.