Pictures are cardboard prototype.
I don't have a lot of time to spend on the project and also i don't know much about product development nor electronics. A community effort would be great !
My research has led me to Raphnet's usb_game12 PCB that could be used with an ATMEGA8 on a TQFP package. To achieve very flat buttons the best one i have identified are the GBA SP ones, with tactile dome switches.
Open topics:
- could shoulder buttons work or should they be on the front face ?
- does having an always plugged in gamepad affect battery life ?