It's a big button for push to talk, gaming, whatever. Step on it, sit on it, elbow it.

Micro switch taken from an old mouse. Designed around this particular microcontroller:

[Type-C USB Pro Micro ATmega32U4 5V 16MHz](https://www.amazon.com/dp/B0BCW67NJP?psc=1&ref=ppx_yo2ov_dt_b_product_details). YMMV regarding fitment if using a different MCU.