A junior at Brown and a creative writing major from Brooklyn, Mr. Last has been making crossword puzzles since he was in high school, and he was, for a time, the youngest constructor ever to have a puzzle in The New York Times. Eventually, The Times’s puzzle editor, Will Shortz, took him on as an intern. His crosswords were “extraordinary,” Mr. Shortz said in an interview, especially for someone so young.

I’ve wasted my life.