Dollar Tree has everything in the store priced at $1. I pick up a plethora of Sudoku and crossword puzzle books often. Most of the Sudoku books have 4 levels of puzzles. I will do two '1 star' puzzles. Then, two '2 star' puzzles. Followed by two '3 star' and two '4 star'. Will go back and start over, using that progression until the book is completely done. I have a Sudoku and/or a crossword book under the sink in the bathroom. While entertaining my "morning constitutional' is when I turn out a lot of puzzle work. If I get bored with the computer, I'll quite often work on Sudoku or crosswords in the evening. I feel working those puzzles will assist in keeping the mind active.