1. Game Elements:
    Each Crossoku game consists of three main components:
– A Sudoku puzzle,  Nine crossword-like clues, and Nine key letters that correspond to the crossword answers.

2. Sudoku Rules:
The Sudoku puzzle follows classical 9×9 grid rules, starting with a unique set of initial numbers. All puzzles are rated as difficult.

3. Crossword Clue Answers:
The answers to the crossword clues are determined entirely by the key letters provided. Each key letter is assigned a numerical value that corresponds to the Sudoku. Answers must be placed horizontally or vertically within the Sudoku grid.

4. Fitting Clue Answers into Sudoku:
You are not provided with the exact positions for the crossword answers in the Sudoku grid. Clue answers must be placed without breaking Sudoku rules.

5. Game Progression:
As you place more correct crossword answers, the Sudoku becomes progressively easier. Eventually, you should be able to complete the Sudoku without needing further crossword assistance. Solving all crossword clues will leave you with a simpler Sudoku to finish.

6. Game Assistance:
The Crossoku program provides help in placing the crossword answers into the Sudoku grid.

7. Double Crossoku Version:
In the “Double” version of Crossoku, you solve two Sudoku puzzles that share the same set of clues.

8.  Analog Double Version:
The “Analog Double” version replaces the standard numbers with nine images. You must use these images to evaluate the crossword answers.