Nintendo patented a Game Boy-style casing for capacitive touchscreen devices in the U.S. It consists of a shell that can hold your device and apparently allow you to play Game Boy games. The patent was formally filed on March 16, 2018. One of the key features revealed by the patent is the ability for inputs on the buttons of the casing to be sensed by the touchscreen beneath the buttons. To learn more about this patent, click here.
Source: Siliconera.com