The Penguin Sudoku Challenge: Volume Two

Sudoku (soo-doh-koo): a 9x9 logic puzzle to superheat the very core of your brain and to challenge your numeracy, spacial awareness, and problem-solving abilities. WARNING: the five levels of Penguin Sudoku Challenge: Volume 2 may leave you smugly grinning, scratching your head, sighing deeply, snapping your pencil—and you may even throw your book at the wall. But you also have permission to frame your most difficult completed 9x9s. Good luck!