Just DuoLingo, watching Japanese stuff without subtitles (including cultural guides for further understanding) to force myself to listen, and then looking up words I don’t know when I come across them.
My goal was never to learn how to speak or write anything; just understand it well enough to watch Japanese media in the original language. I still often have to rewind and play back stuff to get it all. Especially if they are saying a long sentence really fast.
It also probably helps that Language itself is one of the things that tickles my autistic brain.
Literally anything. Even the things I still have that use AA and AAA batteries (of which the newest things are my VR controllers which is so stupid…), I have rechargeable lithium ion AAs and AAAs for so I don’t have to constantly buy batteries.
As a kid, tho, I loved 9volts because they had the best connectors. I could take a little battery powered motor apart, glue it to some legos and use it to make machines that moved or did stuff. I almost killed myself once wondering what would happen if I took the cord from a busted fan, wired it to the 9volt battery motor and the plugged the cord into the wall outlet.
It blew up the motor and started a fire. 🤣