# Crossoku. Sudoku X. — Diagonal Sudoku X Challenge > Diagonal Sudoku X Challenge (iPhone/iPad app by MICHAEL CHARLES LOCKYER.) - Source: https://appshunter.io/ios/app/crossoku-sudoku-x/id6759494212 (this page in markdown: same URL + `.md`) - Developer: [MICHAEL CHARLES LOCKYER](https://appshunter.io/developer/1859958591) - Category: Games, Education, Puzzle, Strategy - Price: Free with in-app purchases - Age rating: 4+ - Requires: iOS 13.0 · 153 MB - Languages: British English, Arabic, Catalan, Croatian, Czech, Danish, Dutch, Finnish, Canadian French, German (Germany) and 23 more - Released: 2026-03-23 - Data updated: 2026-08-01 - User reviews in markdown: https://appshunter.io/ios/app/crossoku-sudoku-x/id6759494212/reviews.md ## What is Crossoku. Sudoku X.? Sudoku X — the diagonal twist that changes everything. Crossoku is Diagonal Sudoku (also known as Sudoku X): a 9×9 grid where both main diagonals must also contain digits 1–9 exactly once. That single extra constraint creates 11 constraint regions instead of the standard 9, opening up powerful new solving strategies and making every puzzle feel fresh — even if you have solved thousands of standard Sudoku puzzles. THE DIAGONAL DIFFERENCE • Both main diagonals are full constraint regions, just like rows, columns, and boxes • Diagonal interactions unlock techniques unavailable in standard Sudoku • Puzzles are carefully generated so the diagonal constraint is always meaningful • The same grid, a whole new layer of logic SIX DIFFICULTY LEVELS • Easy: Gentle introduction to diagonal logic — perfect for new players • Medium: Diagonals start shaping every move you make • Hard: Diagonal intersections become critical solving pivots • Expert: Multi-region interactions demand sharp, precise thinking • Pro: Advanced techniques and diagonal chains push your limits • Master: The pinnacle — only the most rigorous logic survives CAMPAIGN MODE • 50 handcrafted puzzles across 5 progressive worlds • Each world introduces a new technique to master • Clear a world to unlock the next challenge • Earn stars and track your solving mastery DAILY CHALLENGES • A fresh diagonal puzzle every day, the same for players worldwide • Build your streak and track your calendar history • Compete on global leaderboards and see how you rank • Push notifications remind you when a new puzzle is waiting TECHNIQUE LIBRARY • Browse and practice diagonal Sudoku techniques interactively • Understand why each move works, not just what to place • Progress from Naked Singles to advanced diagonal eliminations • Smart hints explain the technique behind each nudge ELEGANT DESIGN • Clean, focused aesthetic — no clutter, no distractions • Ten color themes with light and dark variants • Refined typography readable at any size • Smooth animations and a responsive, native feel • Full landscape and portrait orientation support SMART SOLVING TOOLS • Pencil marks to note candidates in any cell • Unlimited undo and redo — explore freely • Optional error highlighting to catch mistakes early • Auto-save so you never lose your progress • Highlight matching numbers to spot patterns instantly TRACK YOUR PROGRESS • XP system with 100 levels to achieve • 60 achievements across 6 categories to unlock • Personal statistics per difficulty level • Win streaks and personal best times • Game Center integration for competing with friends • Cloud sync keeps your progress safe across all devices PLAY YOUR WAY • Fully offline — play anywhere, anytime • No account required to start immediately • 45+ languages supported with full localization • VoiceOver screen reader support for accessibility • High contrast themes for comfortable viewing • No forced tutorials — jump straight into the puzzle • Free to play with no paywalls blocking content If you love Sudoku and want a fresh strategic challenge without learning an entirely new game, Crossoku is for you. The diagonal rules are simple to understand — mastering how to use them is the adventure. Download Crossoku and think diagonally. Terms of Use: https://www.locksmithcreativemilan.com/crossoku/legal/terms-of-service.html ## Pricing and in-app purchases Base price: Free. **Subscriptions** | Subscription | Price | Period | | --- | --- | --- | | Crossoku Premium Monthly | $2.99 | per month | | Crossoku Premium Yearly | $17.99 | per year | ## Version history (last 4 releases) ### 1.2.4 — 2026-04-03 What's New in v1.2.4: - Fixed Google Sign-In not completing on iPad and iPhone - Fixed authentication callback issues - Bug fixes and performance improvements Thank you for playing Crossoku! ### 1.2.3 — 2026-04-01 What's New in v1.2.3: • Enhanced diagonal region visuals — bold contrasting colors across all themes • Share menu now fully visible with proper icon rendering • Updated Reddit sharing with clearer grid format • High contrast mode improvements for diagonal regions • Bug fixes and performance improvements Thank you for playing Crossoku! ### 1.2.2 — 2026-03-27 What's New in v1.2.2: • Enhanced diagonal region visuals — bold contrasting colors across all themes • Share menu now fully visible with proper icon rendering • Updated Reddit sharing with clearer grid format • High contrast mode improvements for diagonal regions • Bug fixes and performance improvements Thank you for playing Crossoku! ### 1.2.0 — 2026-03-23 No release notes. ## More apps by MICHAEL CHARLES LOCKYER - [Sudoku. Simple & Elegant.](https://appshunter.io/ios/app/sudoku-simple-and-elegant/id6756303439) - [Numdoku. Daily Killer Sudoku](https://appshunter.io/ios/app/numdoku-daily-killer-sudoku/id6759094745) - [Windoku. Hyper Sudoku.](https://appshunter.io/ios/app/windoku-hyper-sudoku/id6759494100) - [Jigsoku. Jigsaw Sudoku.](https://appshunter.io/ios/app/jigsoku-jigsaw-sudoku/id6759494350) All apps by MICHAEL CHARLES LOCKYER: https://appshunter.io/developer/1859958591 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-01.*