-Open Steam Deck in Desktop Mode
-Open Firefox (or other browser)
-Go to www.ottoojala.com/soccerphysicssteamdeck/soccerphysics.zip and download the zip file
-From the browser's downloads section (or from your Downloads folder in file manager), click and extract the zip where you want to, for example on the Deck's "Home" folder
-Open the file manager (Dolphin) and open the "SoccerPhysics" folder that is now in the folder you specified
-Double click "SoccerPhysics.x86_64" to open it (you need to do this once in the Desktop Mode to give permissions to run the game)
-The game should now open, but the hardware controls wont by default work with in Desktop Mode
-Tap the "x" button in the upper left corner to close the game
-Go to your downloads folder and delete SoccerPhysics.zip if you want to free up space
-Close the file manager and open Steam, while still in Desktop Mode
-Go to Games -> Add a Non-Steam Game to My Library...
-Go to the folder where you extracted the game (in this case: Home/SoccerPhysics)
-Change the "Filter" from "Applications" to "All files"
-You should now see the file "SoccerPhysics.x86_64" in the folder, select it and click "Open"
-Click "Add Selected Programs"
-You should now have Soccer Physics ready to run in Gaming Mode!
Rename the game to "Soccer Physics" and change the icon
-Select "SoccerPhysics.x86_64" in Steam's Library while in Desktop Mode
-Click on the gear icon and select "Properties..."
-Rename "SoccerPhysics.x86_64" to "Soccer Physics". Note that bringing up the virtual keyboard (Steam button + X) crashes the Deck quite often...
-Click on the gray rectangle next to the game's name
-Go to the folder where the game is installed and select "icon184.png"
-Close the window
Change the banners of the game
-Right click on the big black area behind the game's title
-Select "Set Custom Background"
-Go to the SoccerPhysics folder and select "banner.jpg"
-Right click on the newly set background image and select "Set custom logo"
-Change the "Filter" from "JPEG" to "PNG Image"
-Select and open "logo.png"
-Click the background image once again to select "Adjust Logo Position" and set the logo as you like
-Go to Library view and search for the game, you should see it the "All Games" or "Recent Games" section
-Right click on the gray rectangle that reads "Soccer Physics" and select "Manage -> Set custom artwork"
-Go to the SoccerPhysics folder and select "capsule.jpg"
-Feel free to modify these as you wish! :--)
You're all set! Now return to Gaming Mode, browse to "Non-Steam" section in the menus and play!
Congratulations! You should now have Soccer Physics installed on your Steam Deck :--)
Use the hardware buttons to play and the touch screen buttons to use the menu. You can also restart match by pressing the Deck's start button (the one with the stree strokes).
To delete the game, go back to Desktop Mode and delete the folder "SoccerPhysics".