This is a Gamepad Case for MX Switches (Cherry or Gateron).
It uses a Arduino Pro Micro as controller.
You can finde a part list and step by step instructions on maker-tutorials.com.
Currently only in german.
The case has clip connection, or you can use screws (3x M3x12).
If you have any suggestion, please write a comment.
Buy parts (affiliate links):
The case is designed in Fusion 360.