X Sudoku is also called diagonal sudoku. It is another type of 9x9 sudoku. Based on regular Sudoku, diagonal sudoku has more requirements. The two grey diagonal lines have to contain all numbers from 1 to 9. Since diagonal sudoku has more rules, the solving process is more challenging and intriguing. Practice scanning the diagonal regularly rather than just the rows, columns and blocks to help you make progress. It is the difference between X sudoku and regular sudoku.
If you don’t want to measure time, you can turn it off with the small x next to the clock. You can adjust the size of the sudoku board by selecting small / medium / large. When you have filled in all the fields, press the "I'm ready" button! It will allow you to check that you have worked well. Pressing the "new game" button will clear the numbers you have entered so far and gives you a new board.
This online game is free and also works on smartphones. Recommended for travellers on public transport, for those who are waiting or just needing headwork, for those who want to compete or just solve logic puzzles, and for those who need culturally useful developer fun.