Yet Another "What's a good project to work on?", but for a 40 hr road trip with little to no internet.

I'm helping my sibling move from Washington to Alabama (USA). The trip is close to 40hrs driving time.

I've done some rust projects so far (discord bot, axum api service, etc), but i'm wondering what is a good project to work on while I'm riding as a passenger. I'm not really going to have any internet. There may be internet at some motels, but I don't have much hope for that.