How about solving a sudoku? E.g. https://www.nytimes.com/puzzles/sudoku https://www.nytimes.com/puzzles/sudoku - choose the level so it takes you less than 10 m

How about solving a sudoku? E.g. https://www.nytimes.com/puzzles/sudoku https://www.nytimes.com/puzzles/sudoku - choose the level so it takes you less than 10 minutes.