We included the ATTiny85 chip with an on-board USB programmer which simply plugs into the learning kit making it easy to make connections and prototype your projects.

His hardware board is exceedingly simple, just an ATtiny 2313, a USB port, and a handful of other components, but allows [Ben] to receive data on eight pins on a breadboard and send them over USB ...

For USB serial programming, GGtag uses the Web Serial API through the web interface at ggtag.io. The device can emulate 125 kHz RFID tags through an ATtiny85 MCU and the avrfid firmware.