We've often made little robots or games and we need a quick and small gamepad-like interface to control motors or robots or whatever. this gamepad will do nicely: it has an analog thumb-stick, and six buttons: A B X Y and select start. the two analog readings and six digital readings are managed by an onboard seesaw peripheral https://github.com/adafruit/Adafruit_seesawPeripheral attiny816 - so once the PCBs are assembled we gotta program that chip. we made a programming shield with a metro m0 https://www.adafruit.com/product/3505 and OLED screen. we use an M0 because we need a fair amount of memory to store the firmware of the target board in flash, plus solid hardware serial support to perform the UPDI program. the screen lets you know when its time to test the buttons by pressing them, in a few seconds we're done!