A sudoku was a number-based puzzle which was solved with pen and paper. Sudokus of various difficulties were printed in the local newspaper of Winchelham. (PROSE: I Am a Dalek [+]Gareth Roberts, Quick Reads (BBC Books, 2006).)
Within the sphere chamber, Rajesh Singh reported to Yvonne Hartman that he was on "Sudoku book 509". (TV: Army of Ghosts [+]Russell T Davies, Doctor Who series 2 (BBC One, 2006).)
At the end of a long day, Colin Colchester-Price relaxed by doing Sudoku. (AUDIO: A Kill to a View [+]Mac Rogers, Aliens Among Us 2 (Aliens Among Us, Big Finish Productions, 2017).)