[Question] Do you have algorithms for passing time productively with only your own mind?

Things that re­quire noth­ing, just you. At least in the short term. (e.g., it’s ok to think about what ques­tion would be worth­while to ask on Less­wrong.) I my­self some­times have spe­cific ques­tions from my stud­ies and/​or prac­ti­cal mat­ters, which are ex­cel­lent for this pur­pose. But the sup­ply of these ques­tions usu­ally is much less than the time I have for pon­der­ing them.