If your game crashes, you can find its error log on your PC, here:

  DRIVE:\Users\USERNAME\AppData\Local\Tunnels_Under_Yorion_May_demo\err_log.txt

If you can upload its contents here, I can try to hunt down the error.

Furthermore, you could download and play the "standalone" version of the game while we figure out what's happening with our save/load system, which appears to be the culprit of a lot of the crash reports.