Hi, I read your post #27 about your library. Does the library have a license ?
Your library with heartbeat in Wokwi simulation: Noiasca Took Kit Heartbeat - Wokwi ESP32, STM32, Arduino Simulator
My millis() example with math in Wokwi simulation: millis_soft_pulsating_led.ino - Wokwi ESP32, STM32, Arduino Simulator (I have another one, which is specifically a heartbeat).
Sketch by runaway_pancake post #81 in Wokwi simulation: millis gamma fade 01 - Wokwi ESP32, STM32, Arduino Simulator
The MakersPortal example (video was mentioned in post #11) with a triangle in Wokwi simulation: Triangle Wave Breathing LED - Wokwi ESP32, STM32, Arduino Simulator