Take an Xbox controller, but split it in two so that a smartphone (maximum 6.7 inch / 17 cm) fits between them. The result is the Nacon MG-X Pro.
This controller is for smartphone games that require more control than just tap and swipe. Nowadays there are more and more, partly due to the rise of streaming.
Stream
You can play games that are actually designed for console and PC on your phone. Provided your wireless internet speed allows it. After 20 hours of play, this gamepad is empty, charging is done via USB-C.
The suggested retail price of the Nacon MG-X Pro is 99.99 euros.