If you just put fgn.cdn.serverable.com/common/flashes/nf/insert_game_name_here, it doesn't seem to work anymore, it would says {"detail":"File not found"} instead of loading the game
It seems to only work if you enter
fgn.cdn.serverable.com/common/flashes/nf/insert_game_name_here/index.html?d=################, which is kind of annoying if you want to switch from one game to another by going through the website and clicking full screen all the time
This is the protection from hotlinking, in other words when other websites do publish direct links to fgn.cdn.serverable.com, they game should not work.
if you copy and paste link directly to browser, e.g:
https://fgn.cdn.serverable.com/common/flashes/nf/difficult_choice/index.html
The game WILL work.
If the website behavior is different, please give me more details, for example game URL.