PCB Art badge using 2020 WS2812B SMD LEDs, attiny45 MCU and light_ws2812 library.
Detailed writeup can be found here
To build the firmware, you need the avr-gcc toolchain and a USBtinyISP (which you can buy for a few euros on AliExpress etc.)
cd firmware
make all
Then, with the programmer connected to the test points on the back of the badge, run:
make fuses
make program
to flash the firmware onto the badge.