LED Heartbeat with varying intensity and pause

This is for Lab 1.4.2, MEAM 5100: Design of Mechatronics course at UPenn.
The video demonstrates gradually increasing and decreasing the duty cycle of PWM signals sent from the ATmega32u4 microcontroller to the LED. The increment and decrement timer is asymmetric, and the two cycles have different max intensities to make it behave like a heartbeat.