At the end of 2021 I started playing with this app and then didn't touch it again until the end of 2022. It may very well be another seasonal project for me to hack on.
SnowFlakes is a Menu Bar app that puts snow or flakes on the screen while you're using your Mac.
demo-480.mov
For each display, a non-interactive overlay window is added. Inside that window is a fullscreen SKView that runs a scene that contains emitters. These emitters spit out snow and flakes and can be tweaked by the user interface. Settings are saved automatically across restarts of the app via SwiftData.