(Challenging Project: A Crossword-Puzzle Generator)   Most people have worked crossword puzzles, but few have ever attempted to generate one by hand. Generating a crossword puzzle is suggested here as a string-manipulation and file-processing project requiring substantial sophistication and effort. There are many issues you must resolve to get even the most straightforward crossword-puzzle-generator application working. For example, how do you represent the grid of squares of a crossword puzzle inside the computer? Consider using a two-dimensional list where each element is one square. Some of those elements will be “black” and some will be “white.” Some of the “white” cells will include a number that corresponds to a number in your across and down clues. You need a source of words (i.e., a computerized dictionary) that can be directly referenced by the script. In what form should these words be stored to facilitate the complex manipulations required by the application? Consider using a Python dictionary for this purpose. You’ll want to generate the clues portion of the puzzle, in which the word definitions for each across and down word are printed. Merely printing a version of the blank puzzle itself is not a simple problem, especially if you’d like the black-squared regions to be symmetric as they often are in published crossword puzzles.