Double-doku (Mensa) : Double-doku means double the fun and double the challenge! These tricky puzzles combine the best of traditional sudoku with acrostic wordplay. Start by solving the clues: each clue is missing its first letter, so you have to figure that out first. Next, write down the answers in the accompanying numbered spaces. Then, place those letters in the correspondingly numbered squares in the grid. Each square comes from two different clues to help you complete it. When the entire grid is filled, there's another fun step: one of the rows will have the answer to the clue hidden in the initial letters of the clue list.