[makeitdouble]

What if I told you there is another plug type, that might still be sold with some old sets somewhere, and is still supported by a bunch of third party hubs (that for a long time were more advanced in many ways than Lego's own system ...)

Lego's stewardship of all this was a mess, and I'm super glad they open the system to officially blessed third parties.

[bombcar]

There's also all the various rail/train systems, some of which are compatible with some variants ...