|app_id||The unique App ID for your game.|
With this function you can open the Steam overlay on the store
page for a game so that users can buy or download DLC (for
example). You need to supply the unique App ID for the game or DLC
which you would get from the Steam dashboard when you set it
The above code polls the keyboard for the F1 key and if it is then Steam overlay will be opened on the page for the game content using the app ID stored in the global variable.