I've seen a few Game Boy phone cases out in the wild - protective cases which (unofficially) make the back of your mobile look like Nintendo's classic handheld.
This is something more than a standard case, with buttons that cleverly react with your device's touchscreen beneath to register commands.
A window in the design lets you see a Game Boy screen-sized portion of your own smartphone - the patent mentions it would be here that the game you are playing is displayed - or you can open up the front of the case to see the rest.
It begs the question - when will Game Boy emulation come to iOS and Android? Because this case looks ready made for it.
Nintendo recently began selling NES-style controllers for the Switch to use with the console's new Online Subscription service, which includes access to more than 20 NES games on demand. A pair of those will cost you Ł50 - hopefully this phone case, if it materialises, will come a little cheaper.