I felt a strong urge to *make* something, for the sake of my mental health.
About a year and a half ago the kid saw a bubble gun in a toy shop and expressed an interest, I said it would be fairly easy to make one, they said "go on then", I bought a bunch of parts, and then failed to do anything further.
This evening I finally dug everything out again and did a breadboard test of all the electromechanical bits. It looks like that side of things will work OK.