ECHO vs Sudoku Sagax
Price, ratings, monetisation and update history for both games, side by side — with what reviewers say about each.
ECHO
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Your echoes are your teammates. ECHO is a time-loop puzzle: every run is recorded, and when you press ECHO, your past self replays it - step by step, loop after loop. Hold plates for each other, open doors across time, and thread paths no single runner could ever take. EASY TO LEARN, DEEP TO MASTER - 100 campaign levels across ten decades, from gentle first steps to choreographed finales - Mechanics that weave together: chained doors, counter-doors, double doors, fragile floors, beat walls, paradox boards and mirror echoes that replay your run backwards - Handcrafted signature levels where every single step must be planned FOUR WAYS TO PLAY - Campaign: 100 levels with a carefully tuned difficulty curve - Daily puzzle: one fresh board every day - keep your streak alive - Zen: endless generated puzzles in six difficulties - Time challenge: how many boards can you solve in one run against the clock? MADE WITH CARE - Completely offline: no account, no ads, no tracking, no data collection - Music is synthesized live on your device - no two sessions sound the same - Home-screen widget that grows with your streak - and hides a secret level - Game Center leaderboards and achievements - Available in 7 languages ECHO is free and complete from the first minute. The only purchases are voluntary tips for the developer - they unlock nothing. Your past self is waiting.
Sudoku Sagax
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Sudoku Sagax is Sudoku with real progression: solve levels, collect points and stars, climb through 19 fox ranks and take on everyone else in the daily challenge. Nona the vixen shows you around and explains every new puzzle type in half a minute. ELEVEN PUZZLE TYPES • Sudoku in four difficulties, from Easy to Extreme • Killer Sudoku, Kakuro, Nonogram, Crowns, Binary puzzle • X-Sudoku, Jigsaw Sudoku, Mini 6x6 and the big 16x16 • Foxhold: Sudoku as tower defence, our very own game Every type has its own levels, its own best times and its own leaderboard. DIFFICULTY BY TECHNIQUE In classic Sudoku, difficulty follows the techniques a puzzle calls for, not the number of givens: Easy needs singles, Extreme asks for X-Wing and XY-Wing. In the game you see which technique is needed, and after a win, what you solved it with. Every level of every puzzle type can be solved without guessing, with logic alone. DAILY CHALLENGE AND STREAKS One puzzle a day, the same for everyone, with its own daily leaderboard. Solve on consecutive days and your streak grows. Streak shields cover a missed day, so a busy calendar does not undo weeks of work. RANKS, STARS, ACHIEVEMENTS Every solved level counts towards your rank: 19 tiers from Fox Cub to Sagax Immortalis, each with its own fox portrait as a profile picture. Add up to three stars per level and 39 achievements. DUELS AGAINST FRIENDS After a win, challenge someone with a link: they play exactly the same puzzle against your time. No account needed on their side. THOUGHT THROUGH IN DETAIL • A tip that shows you the next technique instead of giving away the digit, plus notes, eraser and undo • Mistakes shown instantly or only at the end, your choice • Digit-first mode for fast entry • Light and dark themes, in ten languages • Puzzles are generated locally, so a dead spot will not stop you You can start playing without an account. With a free account (sign in with Google or Apple), your progress, streak and leaderboard position follow you across devices, including between app and browser. Sudoku Sagax is free, with no ads and no in-app purchases. The den is open. How far will you get?
Screenshots
Verdict
The clearest difference is device support: Sudoku Sagax at 3 against ECHO's 1. Sudoku Sagax also leads on iOS requirement (15.0 vs 17.0). On price, update cadence, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
ECHO ships an update every 3 days, Sudoku Sagax every 2 days. The most recent releases landed on October 5, 2026 and October 18, 2026 respectively.
| Parameter | ECHO | Sudoku Sagax |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 3 days | Every 2 days — better |
| Ads | No | No |
| In-app purchases | No | No |
| Devices | iPhone | iPhone, iPad, iPod — better |
| Requires iOS | 17.0 | 15.0 — better |
| Further details — not scored | ||
| Size | 3 MB | 17 MB |
| Age rating | 4+ | 12+ |
| Developer | Lucas Hesseldieck | Vulpes Sagax UG (haftungsbeschränkt) |
In-app purchases
ECHO
No in-app purchases
Sudoku Sagax
No in-app purchases









