A magic plugin for the Decky Loader that overlays the screen with black color, emulating the screen being turned off on the Steam Deck OLED.
- Install Decky Loader
- Switch to steam game mode
- Press
- Go to the tab
- In the upper right corner, click
- Find MagicBlack in the plugin list or search for it
- Press the Install button
Now that you have MagicBlack, press 
to overlay a black background over the entire screen.