I had a friend in high school who brought in the Tesla coil he made with among other things a PSU from an old computer.

I pestered that kid so hard about DC-DC voltage regulators and he did not know enough electronics to design one from first principles. I think ladder circuits was as far as he got. But I wanted step-down not step-up transformers.

15 years later when the first gen of really good LED flashlights with built-in voltage regulators popped up I owned at least one at all times.