When your mouse runs out of battery during a game, you...

Never use battery peripherals while playing a game that matters to you. I don't have anything that isn't wired.

If you are not used to play on a touchscreen it probably ends badly.
I never used my wireless mouse for chess. Despite the problems with defect cables all the time I prefer a very small notebook mouse.

Bro connect it to your brain. Your brain has enough ppower
You’d have to make a hole big enough in your head through your scull to have the usb direct access to your brain. Lots of tissue to remove, lots of blood to sop up, lots of bone to saw through. I suggest a stick to bite down on.
Has this ever happened to you - what did you do?