1. Start the game. Once the launcher appears, choose Settings.


2. On Common tab, find Use SSE Display Tweaks. Make sure it is ticked.


3. On the same tab, find Aspect Ratio and click on it.
4. Select User-defined from the drop-down menu.


5. Now look for Resolution on the same tab. Click on it.
6. Enter your screen resolution, e. g. 1920 x 1080. Make sure there's a space before and after the x.


7. Click on Save settings.

1. Open the game in your library.
2. Open the settings (cogwheel icon).
3. Select Properties... > General > Launch options.


4. Write fullscreen in the prompt line. Close the window. Settings will be saved automatically.


5. Launch the game.