There are common crossword variants that vary more from a regular crossword than just an unusual grid shape or unusual clues. These crossword variants may be based on different solving principles and require a different solving skill set. They end up having a more unique crossword puzzle answers.
Cipher crosswords were invented in Germany in the 19th century. Published under various trade names, and not to be confused with cryptic crosswords, a cipher crossword replaces the clues for each entry with clues for each white cell of the grid – an integer from 1 to 26 inclusive is printed in the corner of each. The objective, as any other crossword, is to determine the proper letter for each cell; in a cipher crossword, the 26 numbers serve as a cipher for those letters: cells that share matching numbers are filled with matching letters, and no two numbers stand for the same letter. All resultant entries must be valid words. Usually, at least one number’s letter is given at the outset. English-language cipher crosswords are nearly always pangrammatic (all letters of the alphabet appear in the solution). As these puzzles are closer to codes than quizzes, they require a different skill set. Many basic cryptographic techniques, such as determining likely vowels, are key to solving these.
In a diagram-less crossword, a skeleton crossword or carte blanche, the grid offers overall dimensions, but the locations of most of the clue numbers and shaded squares are unspecified. A solver must deduce not only the answers to individual clues but how to fit together partially built-up clumps of answers into larger clumps with properly set shaded squares. Some of these puzzles follow the traditional symmetry rule, others have left-right mirror symmetry, and others have greater levels of symmetry or outlines suggesting other shapes. If the symmetry of the grid is given, the solver can use it to his/her advantage.
In a variation of this puzzle, the clues are not individually numbered but given in terms of the rows and columns of the grid, which has rectangular symmetry. The list of clues gives hints of the locations of some of the shaded squares even before one starts solving them. For an instance, there must be a shaded square where a row having no clues intersects a column having no clues.
A fill-in crossword features a grid and the full list of words to be entered in that grid but does not give explicit clues for where each word goes. The challenge is figuring out how to integrate the list of words together within the grid so that all intersections of words are valid. Fill-in crosswords may often have longer word length than regular crosswords to make the crossword easier to solve, and symmetry is often disregarded. Finding these types of crossword quiz answers and crossword puzzle answers are also used to demonstrate artificial intelligence abilities, such as finding solutions to the puzzle based on a set of determined constraints.