A Number-Logic Puzzle is a type of puzzle that requires the solver to use logic and numbers to solve it. The most popular type of Number-Logic Puzzle is Sudoku, which is a 6 letter word. Sudoku involves filling in a 9x9 grid with numbers so that each row, column, and 3x3 box contains all of the digits from 1 to 9. It is a challenging yet rewarding puzzle that can be enjoyed by people of all ages.