It's not the most complicated, but it's nice.

Ceiling motion sensor above the stairwell leading to second floor that activates hue bulbs in the upstairs hall. Depending on the time of day it turns on for different lengths of times/brightness and at night for ~2 min to red to allow easy travel without upsetting eyes adjusted for darkness.

That and a similar one that we activate via our echos called "Bedtime for babies" that dims all the lights to have our little one start winding down.

If you live near a microcenter pretty frequently they run deals that have ender 3s for pretty cheap if you've never been a customer before. Usually a coupon.