I think we have a solution for the black screen in game problem (the kind where you find a code guard report in the log file; not the one caused by driver issues).

Anyway, it seems that the executable is messed up for some users! (Found that with the help from a former intern of ours who was (un)lucky enough to have this problem :))

The fix:

1. Use the steam client to verify game cache (right click on the game in library, select properties, select the "Local files" tab, click the "Verify integrity of game cache.." button)
2. Note if something was downloaded
3. Start the game again and see if the black screen persists

If this didn't help (nothing was re-downloaded during verification process), try the steps again with another step before them:
0. Delete the Talos_Demo.exe from your steam folder:

<steam root folder (for example c:\Program Files\Steam)> \steamapps\common\The Talos Principle Public Test\Bin\Talos_Demo.exe
repeat the steps 1-3 again

New exe should be downloaded and if you're not very unlucky (if you are, try the steps 0-3 again once more) it should work.

Please let us know if this helps.