It is relatively easy for the parties to exclude the postal rule: in typical American-style crossword puzzles, the theme is first created, because a series of long symmetrical across responses are needed around which the grid can be created.   Since the grid typically exhibits 180-degree rotation symmetry, the answers should also be: Therefore, a typical 15×15 square American puzzle may have two 15-letter entries and two 13-letter entries that could be appropriately arranged in the grid (e.g. B one entry of 15 letters in the third line and the other symmetrically in the 13th line; one entry of 13 letters, which begins in the first square of the 6th line) and the other ends in the last square of the 10th row).   The subject must not only be funny or interesting, but also coherent internally. . . .