Sudoku X: Diagonal Prophecy – Play Free Online
Play Sudoku X: Diagonal Prophecy, a premium diagonal Sudoku game where the numbers 1–9 must appear exactly once in every row, column, 3×3 box, and both highlighted corner-to-corner diagonals.
Explore 300 campaign missions, complete a new daily challenge, choose from five difficulty levels, use smart notes and logical hints, unlock achievements, and enjoy responsive controls designed for desktop, tablet, and mobile devices.
Sudoku X: Diagonal Prophecy Features
- Complete Sudoku X rules with two additional diagonal constraints
- 300 campaign missions across ten celestial worlds
- Five difficulty levels from beginner to extreme
- Quick Play, Daily Challenge, Zen Mode, and Eclipse Rush
- Smart Hint system with logical explanations
- Diagonal-aware candidate notes and automatic notes
- Undo, redo, erase, and automatic progress saving
- Achievements, campaign stars, ranks, statistics, and daily streaks
- Three visual themes and polished animations
- Mouse, keyboard, touch, and mobile-friendly controls
How to Play Sudoku X
The objective is to fill the entire 9×9 grid with the numbers 1–9. Sudoku X follows the traditional Sudoku rules and adds one important challenge: both long diagonals must also contain every number exactly once.
- Place the numbers 1–9 so no number repeats in any row.
- Make sure no number repeats in any column.
- Complete each outlined 3×3 box using the numbers 1–9 exactly once.
- Complete the main diagonal from the top-left to the bottom-right.
- Complete the second diagonal from the top-right to the bottom-left.
- Fill every empty cell correctly to complete the puzzle.
What Makes Sudoku X Different?
Standard Sudoku uses rows, columns, and 3×3 boxes. Sudoku X adds two highlighted diagonal lines. Every number from 1 through 9 must appear exactly once on each diagonal, creating additional restrictions and new solving opportunities.
A cell located on a diagonal must satisfy four constraints at the same time: its row, its column, its 3×3 box, and its diagonal. The center cell belongs to both diagonals, making it one of the most strategically important cells on the board.
Game Modes
Celestial Journey
Progress through 300 missions divided into ten worlds. Later missions contain fewer starting numbers and require more advanced diagonal deductions.
Quick Play
Select one of five difficulty levels and start a fresh Sudoku X puzzle immediately.
Daily Challenge
Solve a special shared puzzle that changes every day. Complete daily challenges to build your streak and improve your statistics.
Zen Mode
Play without a timer or mistake limit for a relaxed and pressure-free solving experience.
Eclipse Rush
Complete a diagonal Sudoku puzzle before the ten-minute timer reaches zero.
Sudoku X Strategy Tips
- Scan both diagonals before analysing ordinary rows and columns.
- Pay special attention to the center cell because it belongs to both diagonals.
- Use diagonal restrictions to eliminate candidates inside 3×3 boxes.
- Look for cells that have only one valid candidate remaining.
- Use notes for difficult puzzles instead of guessing.
- Recheck diagonal cells whenever a new number is placed on either glowing line.
- Use undo to explore a different logical path without restarting the puzzle.
- Save hints for situations where no direct single candidate is visible.
Game Controls
- Click or tap an empty cell to select it.
- Choose a number from the number pad to place it.
- Enable Notes mode to enter candidate numbers.
- Use Undo and Redo to move backward or forward through your actions.
- Use Erase to clear the selected non-given cell.
- Use Smart Hint to receive a logical clue.
- Keyboard players can use numbers 1–9, N for notes, Z for undo, H for hint, and P for pause.
Frequently Asked Questions
Is Sudoku X free to play?
Yes. Sudoku X: Diagonal Prophecy can be played online for free directly in your web browser.
What is the difference between Sudoku and Sudoku X?
Sudoku X includes all classic Sudoku rules and adds two diagonals that must each contain the numbers 1–9 exactly once.
Does the center cell belong to both diagonals?
Yes. The center cell is part of both highlighted diagonals and must satisfy both diagonal constraints.
Can I play Sudoku X on a mobile phone?
Yes. The game is responsive and includes touch controls for smartphones and tablets.
Does the game save my progress?
Yes. Your current puzzle, campaign progress, settings, achievements, and statistics are saved locally in your browser.
How many levels are included?
The Celestial Journey contains 300 campaign missions across ten themed worlds.
Play Sudoku X Online
Start a new diagonal Sudoku puzzle, follow the two glowing prophecy lines, and complete every row, column, box, and diagonal with the numbers 1–9.
