If you are having issues with Auralux: Constellations on Steam, then please try the following:

1. Launch Steam and navigate to the Auralux: Constellations page in your Library.

2. Select the Manage Settings gear icon to the right of your Achievements.

3. Select Properties...

4. Select the Local Files tab.

5. Select Verify Integrity of Game Files...

6. This should fix any issues you're having.