The Xenko open source game engine ( previously covered here, here and in tutorial form when it was still called Paradox here ) just released a complete game demo called Starbreach. The demo was demonstrated at GDC 2017 and was recently updated to the current version of Xenko and has been released with full source and assets.
Details of the Starbreach demo from the Xenko blog:
Hi everyone, Silicon Studio agreed to release the Starbreach demo from GDC 2017, along with all associated assets as open source (see license), for the Xenko community to use. Code in the project is released under an MIT license, the assets are released under a attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.
Starbreach was originally developed as the Xenko GDC demo for 2016 by Silicon Studio with art support from N-iX production studios. Virgile Bello (xen), Xenko’s lead developer has spent a chunk of time updating the demo and assets to work with the latest release of the Xenko.
You can find the demo and assets here: https://github.com/xenko3d/Starbreach
Check out the demo in action and learn how to get started in the video below.