The goal was to turn a NES controller into a handheld controller to play chip 8 roms.
Even if there is not 16 keys like the chip 8, all keys are not always used. In order to have a bit of control over the keys, I implemented a system to map a controller key to a chip 8 key for each rom. This way when adding a new rom we can configure the appropriate keys.

To be honest, it was a bit tricky to fit everything inside the controller.
That's why there is a USB-C cable to power the device.

For the hardware I used an "Arduino Nano ESP32" which is really thin and can fit into the NES controller.
For the display I used an "OLED 128x64px for 0,96inches" which is the smallest I found. The resolution is perfect because the chip 8 resolution is 64x32 which fits perfectly.
The device is lacking sound as well but it could be done in a later version.