Quick project last night to upgrade a skull with flickering red eyes. Steph had properly themed bouncy balls to go in the eye sockets. I added some red LEDs and an ATTiny13.
I borrowed two different code snippets to make it blink with a nicer look.
Hackaday Link for project 1 (used the LCG formula)
Zenlogic’s PWM code (modified to use only two outputs)