You actually can: The Puya PY32 ranges from about $0.08 on up (well, $0.15 if you only want to buy 5, but the cheapest one is $0.0959 in qty 200 and $0.0676 in qty 5000+). ARM Cortex m0 in a 10-pin ESSOP-10 surface mount package: https://lcsc.com/product-detail/Microcontrollers-MCU-MPU-SOC...

Kind of mind-blowing. 24mhz 32-bit computer for under a dime.

But you'll learn more about the analog-ish world and not need to deal with SMD if you go the 555 route. And it'll save you power vs the astable monovibrator with NPN transistors.

555s are so much fun. It's bananas how much you can do with that chip and a few dirt-cheap resistors and capacitors.

Make has a really nice little book where they walk you through some simple projects on a breadboard with 555s, transistors, etc. https://www.amazon.com/How-Use-Breadboard-Make-Handbook/dp/1...