It’s pretty impressive, especially since he used an ATtiny13 microcontroller. That chip uses an 8-pin dip package, offering only five I/O pins (six if you use the reset pin) and 1k of ...

It’s a strange chip though, with capabilities ... In particular, the GND pin is where the VCC pin is located on other ATtiny chips(!). It pays to read the datasheets. Although we’re grumpy ...