Blinker
This is a project to create an electronic device that should continue to operate from solar power for a long time - hopefully a few hundred years.
I stalled out on the glass sphere project. It was too hard to make the glass nice, and get the surfaces wringably flat, and I had serious doubts about the strength of glass I was going to be able to produce.
Several years passed and I scaled back my ambitions. I decided I would make the enclosure out of metal, with a glass window for light to get in and hit the solar panel to provide energy for the system. Output would be via a single LED that would blink Morse coded messages. I think I'll be able to realistically carry this project through to completion.