Downward, the 1st-person parkour game with interesting setting is currently in EarlyAccess and already looks beautiful - thanks to UE4-engine.

According to the developer Caracal Games there will be a version for Linux next week:

Yes you are right, we plan to expand to Linux in the next week! For Mac we will need to wait a bit more, more updates on this later on!

You have to take a look at the Videos on their Steam page!

Downward on Steam: http://store.steampowered.com/app/506900