But [Martin Held] built a super simple LED Christmas tree ornament using the ATSAME51 series micro-controller, which he regularly works with and had on hand, and lots of bi-color LEDs. He already ...

Inside, an Arduino Nano is hooked up to a series of WS2812b LEDs. The LEDs are flashed in time with the heartbeat of the person holding the heart, thanks to a MAX30102 heartbeat sensor.

Since the Arduino series has an open-source hardware license ... For instance, you can combine an Arduino with LEDs, resistors, sensors, breadboards, and other circuitry components to build ...