Trying to get my head around minecarts, i built my first ever working repeater. Now if only i had an idea what to do with a reliable repeat signal - i can make a bridge extend/retract and fling boulders around, but there's little use for that in an accessless fort(*). The second loop was initially very short, so the plate would never reset - such a system could be used as a dead man's switch, to make something happen once the cart stops cycling. After a child wandered onto the track, i revamped both loops anyway. The child is still hobbling around on a crutch because of a broken ankle, but hasn't suffered lasting damage.
And i finished what caused that mishap - connecting the power train from the highest to the lowest level of the fort, all 140 levels of it. Now i have power both at the mill in the food preparation area and down by the magma sea. I have nothing that actually uses power down there, but if i ever want to pump magma or something, it can be done.
(*) Motto: Who needs migration? We make our own dwarfs.
Set population cap low enough that only the first-year migrants showed up, then went underground and walled ourselves in. We've passed 120 beards by now, and the children of the first settlers are starting to make babies, too.
Edit instead of double-post: and on the volcano fort, i learnt that pumped magma is pressurised. Fortunately, i could get someone to deconstruct the windmill before the flash flood reached my gates. And after some thought, i built a magma cannon. Including a reservoir one z-level higher than the 'barrel' as 'pressure booster' - yes, i know it doesn't work like this. The only thing i can aim it at is the trade depot, though, and i only get dwarven caravans. I guess i'll _maybe_ just pull the lever on a branched save, to see it in action. And i was offered a barony, which i didn't expect. I hadn't checked personalities to settle on a candidate, so my reasoning was that two lye makers in a fort that hadn't produced a single bucket of lye yet was preposterous. Thus, one of them became baron, and i disabled all his jobs apart from hauling and lye-related stuff, to make sure that once he dies, he'll be buried as a lye maker.