Comparison

Extreme Addition vs Rondo

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Extreme Addition

This game offers a unique approach to addition, challenging players to boost their mental calculation skills. It features three levels with increasing number complexity and timed rounds to improve speed and reasoning. The game aims to build confidence and concentration through engaging number practice.

Highlights
  • Unique addition mechanics
  • Boosts mental calculation
  • Improves speed and reasoning
  • Three difficulty levels
  • Timed rounds for score saving
  • Enhances concentration and confidence
Read full description

Extreme Addition® is a unique and extraordinarily simple game that takes you into the world of extreme additions. You will love this game. You will boost your mental calculation and your mastery of numbers. You will gain speed of execution and reasoning. You will create automatisms. You will boost your concentration and motivation. You will gain confidence in yourself. You will not waste your time. Are you ready? So let's go! In this 3-level game, two numbers are presented to you each turn. There are 10 rounds in a game and your time is timed and saved if you have 10/10. You must add these two numbers in an extreme way. You give your answer by pressing one of the 9 digits. The answer is always a number between 1 and 9. At level 1, the two numbers presented are between 1 and 10. (8 + 7) is equal to 6 in the world of Extreme Addition®. Why? Because (8 + 7) = 15, then you separate 15 into (1 + 5) = 6 At level 2, the two numbers presented are between 10 and 99. (28 + 32) is equal to 6 in the world of Extreme Addition®. Why? Because (28 + 32) = 60, then you separate 60 into (6 + 0) = 6 At level 3, the two numbers presented are between 100 and 999. (102 + 108) is equal to 3 in the world of Extreme Addition®. Why? Because (102 + 108) = 210, then you separate 210 into (2 + 1 + 0) = 3 Will you take up the challenge? Mental arithmetic is the daily maintenance of all your mental faculties! Here are some tips to save time in your extreme additions: Tip 1 The result of adding a two-digit number with 9 is quickly obtained from this number as follows: - The number of units minus 1. - The tens digit plus 1. Examples: (25 + 9) = 34 (46 + 9) = 55 (78 + 9) = 87 Tip 2 The result of the extreme addition of 9 with any number from 1 to 9 equals that number. Examples: (4 + 9) => 4 because (4 + 9) = 13 and (1 + 3) = 4 (2 + 9) => 2 because (2 + 9) = 11 and (1 + 1) = 2 (7 + 9) => 7 because (7 + 9) = 16 and (1 + 6) = 7 (9 + 9) => 9 because (9 + 9) = 19 and (1 + 8) = 9 Tip 3 It is faster to add 245 + 637 to the extreme by doing 2 + 4 + 5 + 6 + 3 + 7. Tip 4 Try to get a maximum of 9 in the longest additions, in order to apply tip # 2. Here are all the additions to get the number 9: 1 + 8 = 9 2 + 7 = 9 3 + 6 = 9 4 + 5 = 9 Tip 5 Learn by heart your addition tables, so you no longer have to rely on your fingers to find the result! Lol. 7 + 5 = 12 8 + 4 = 12 6 + 7 = 13 8 + 5 = 13 8 + 6 = 14 7 + 8 = 15 etc ... Be positive, combative, don't give up after a single game, have fun and progress. (This game is available for WatchOS, iOS, MacOS and Apple TV)

About

Rondo

Explore the mathematical beauty of numbers through interactive, animated factorization diagrams. Watch numbers dance, hear their unique songs, and even visualize them in augmented reality. Discover the stories behind special numbers and personalize your experience with customizable palettes and sounds.

Highlights
  • Animated factorization diagrams
  • Augmented reality number visualization
  • Auditory representation of factors
  • Interactive number exploration
  • Field Guide for special numbers
  • Home screen and Apple Watch widgets
  • Customizable color palettes and sounds
Features
Read full description

Rondo turns the counting numbers into a quiet, hypnotic dance. Every number from 1 upward is drawn as a factorization diagram: nested rings of colored dots that show, at a glance, how that number is built from its prime factors. 6 is two groups of three. 12 is three groups of four. Primes can't be split, so they shimmer alone. Then the diagram melts and re-forms into the next number, and the next, an endless looping dance of arithmetic. It's equal parts math toy, teaching tool, and ambient art. WATCH, OR EXPLORE • Let it play for a calm, continuous dance from one number to the next • Tap to pause, drag to scrub to any number, or step one at a time • Speed it up, or slow it right down • A gentle haptic tap each time the dance lands on a prime • Follow any number down its Collatz orbit, and watch it fall back to 1 HEAR IT • Every number sings its factorization: a prime is a single pure tone, a composite a chord of its prime factors • On by default, off whenever you like POINT YOUR CAMERA • Aim Rondo at any printed number and watch its diagram bloom over the page, in augmented reality • Lift a number's diagram off the page and into the room, then walk around it • Street signs, receipts, book pages: factor the world around you EVERY NUMBER HAS A STORY • Tap any number to see what makes it special: whether it's prime, a perfect number, a power, and more • Collect the special numbers you find in the Field Guide SEE THE MATH • The current number and its factorization, always in view • Full VoiceOver support and a spoken read-out of each number and how it factors • Save the numbers you love to Favorites, and share any diagram as an image ON YOUR HOME SCREEN AND WRIST • Widgets that turn today's date into factorization diagrams, across the Home Screen, Lock Screen, and StandBy • A factorization calendar for the month or the current week • A widget for a number you pin, and a stepper widget you tap to walk one number at a time • An Apple Watch app: scrub through the numbers with the Digital Crown, with the same prime haptics • Ask Siri for a number, or add Rondo to a Shortcut • An optional nudge on days whose number is itself worth a look MAKE IT YOURS WITH RONDO PRO A one-time unlock, never a subscription. The full dance stays free. Pro is for going deeper: • New color palettes, backgrounds, and color styles • Layout options for how the rings nest and order themselves • A living clock face that factors the time • Number sequences: count by multiples, primes only, Fibonacci, and more • The full instrument: tune the scale, voice, and space of the sound • Hear any number's story narrated aloud, in your choice of tone CALM BY DESIGN No ads. No tracking. No account. No subscription. Rondo is free to play, with an optional one-time Pro unlock. A LOVING HOMAGE Rondo is a faithful tribute to Brent Yorgey's factorization diagrams and Stephen Von Worley's animated "Factor Conga," built natively for iPhone, iPad, and Apple Watch. The diagrams honor their work; the sound, the augmented reality, and the stories are Rondo's own. Full credits are in the app.

Screenshots

Extreme Addition4 screens
Rondo4 screens

Verdict

The call

The clearest difference is in-app purchases: Extreme Addition at none against Rondo's 5. Extreme Addition also leads on device support (6 vs 3) and iOS requirement (15.6 vs 26.0). Rondo's advantage is update cadence (every 4 days vs every 3 weeks). On price and ads 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

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Rondo sells 5 one-off in-app purchases. Extreme Addition asks for nothing beyond the download.

UpkeepUpdate frequency

Extreme Addition ships an update every 3 weeks, Rondo every 4 days. The most recent releases landed on October 20, 2026 and October 16, 2026 respectively.

Scorecard5 real differences · 5 level
Extreme Addition versus Rondo: the parameters behind the verdict, then further details
ParameterExtreme AdditionRondo
PriceFreeFree
Rating—5.0 (1 ratings) — better
Positive reviews100.0% of reviews—
Number of ratings—1 — better
Update frequencyEvery 3 weeksEvery 4 days — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPad, iPod, Mac, Apple TV, Apple Watch — betteriPhone, iPad, Apple Watch
Requires iOS15.6 — better26.0
Further details — not scored
Size65 MB8 MB
Age rating4+4+
DeveloperBARTOLI JOHANKEN TOMINAGA

Customer experience

Extreme Addition

Written reviews2 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Rondo

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

Extreme Addition

No in-app purchases

5 purchases

Rondo

One-time5
  • Tip a prime · 199$1.99
  • Tip a prime · 499$4.99
  • Rondo Pro$4.99
Show 2 more
  • Tip a prime · 599$5.99
  • Tip a prime · 1999$19.99

Questions

Is Extreme Addition free?
Extreme Addition is free to download, with no in-app purchases.
Is Rondo free?
Rondo is free to download, with in-app purchases available.
Do Extreme Addition or Rondo have ads?
Neither Extreme Addition nor Rondo shows ads.
Which is updated more often, Extreme Addition or Rondo?
Extreme Addition ships an update every 3 weeks, and Rondo every 4 days. Most recently, Extreme Addition was updated on October 20, 2026 and Rondo on October 16, 2026.

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