# One By One: Mental Math — Ace SAT, Algebra & Calculus

> Retro math study game for middle/high school, covering arithmetic to calculus. (iPhone/iPad app by Brice Brown.)

- Source: https://appshunter.io/ios/app/one-by-one-mental-math/id1555846023 (this page in markdown: same URL + `.md`)
- Developer: [Brice Brown](https://appshunter.io/developer/1555846025)
- Category: Games, Education, Puzzle, Strategy
- Price: Free with in-app purchases
- Rating: 4.80/5 from 77 App Store ratings · 22 written reviews indexed
- Age rating: 4+
- Requires: iOS 15.0 · 64 MB
- Languages: American English
- Released: 2021-04-12
- Data updated: 2026-09-09
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/one-by-one-mental-math/id1555846023/reviews.md

## What is One By One?

One By One is a retro math study game built for middle and high school students looking to level up their mental math skills. Featuring randomly generated problems, the app lets you switch from basic arithmetic to advanced calculus. You can also target specific practice areas using the One By One Battles mode or the premium Sandbox mode.

Key Features
Retro Calculator Aesthetic: Enjoy a nostalgic UI designed with classic Unicode and ASCII art, complete with satisfying mechanical key clicks and atmospheric background music.  

Four Math Disciplines: Practice everything from basic arithmetic and high school algebra to trigonometric functions (complete with a built-in unit circle) and calculus derivatives.  

Leveling System: Progress all the way from Level 1 to 99, unlocking brand-new question tiers every ten levels.  

AI Battles & Training: Test your speed in targeted training modes or race against AI opponents to earn in-game rewards.  

Artifacts & Upgrades: Solve rare "Golden Problems" to collect 25 unique math artifacts featuring 9 distinct upgrades to shape your strategy.  

Leaderboards & Achievements: Compete across 5 specialized leaderboards, including a balance-based leaderboard, and uncover hidden achievements.  

Download One By One and start solving math faster than your teacher!

Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

## Key features

- Randomly generated math problems
- Leveling system with unlockable content
- Practice arithmetic, algebra, trigonometry, and calculus
- Retro ASCII art and music style
- Leaderboards and achievements
- Math artifacts and upgrades
- AI battle mode for targeted practice

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Monthly Support | $1.99 | per month |
| Yearly Support | $12.99 | per year |

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Lifetime Supporter pass | $19.99 | one-time |


## Recent user reviews (10 of 22)

All indexed reviews: https://appshunter.io/ios/app/one-by-one-mental-math/id1555846023/reviews.md

### 4/5 — Incorrect Calculation?

*2024-02-06*

tan(5pi/6) is wrong. I’m unsure what the answer has been programmed to be but whatever it is, it’s not accurate. Other than that, great game.

### 3/5 — Almost Perfect

*2023-11-22*

This is a wonderful app and great opportunity for practicing mental math. And this is why I care enough to make a bug report.

Please fix calculus. Some of the answers require infinity, and this is not allowed in the answers. For example, I recently got the question: Given h(x) = 8/x find h’(0). The answer is -∞ as this is the limit from the left and right hand sides, but this is impossible to enter with the ‘Differential Departments’ keyboard. 

One possible stopgap solution would be to make the correct answers available if you pay for a skip (with in-game currency), this way we users can figure out what the game wants in such strange situations. Alternatively, you could take away the questions generating these issues, possibly by plugging all differentiation questions into the Wolfram engine to check the outcomes and then deleting the ones that don’t match. Of course, this won’t work if the questions are auto generated and not drawn from a bank —unless you run all possible questions (which would probably take a long time).

### 5/5 — Love it, want more!

*2023-10-22*

I’ve been having a lot of fun with the app! The derivative and trig section is great practice to knock the rust off my calc now that I’m back in complex analysis. I’d love to see more sections added such as integrals, combinatorics, some kind of series stuff, maybe even some set theory unions and intersections type stuff! I would pay for some extra packs of the sorts! Thanks!

**Developer response:** Wow thank you for the amazing review! It is awesome to see that the app is appealing even for such a high level of math! Those modes would be great to see in the app one day.

### 5/5 — Wonderful math app!!

*2023-07-02*

My free time is so much more productive with this fun app! The way that the problem streaks are timed makes it exciting and the currency system feels rewarding. Using this app is just as fun as other puzzle games but instead of mindless puzzles, it helps you develop practical knowledge! The user interface is also really well done, stable, and easy to use. I reccomended this app to anyone trying to improve their quick math skills! The only gripe that I have is that there isn't an 'explanation' section in the app to refresh my memory on how to do some of these problems. But other than that the app is perfect for math lovers! You won't regret downloading it, especially if you love math! 😄

**Developer response:** Thank you so much for the kind words! I’m glad to see that the focus on making the experience rewarding worked out. I do agree that having a little “manual” for tricks to do the mental math faster would definitely enrich the experience.

### 1/5 — Beware!

*2023-05-21*

Most features are locked. If a kid wants to purchase “Trig Town” the app will attempt to charge $250,000. I’m reporting this to the app store.

**Developer response:** These are just ways to help add progressiom to the game. Everything aspect of the game is FREE to play. By solving problems you get in game money to then purchase the different towns. This helps players build up so they aren’t overwhelmed 
. Sorry for the misunderstanding! 

When developing I thought it might add confusion by making the in game currency represented by $ but I thought this symbol would be easiest to understand. However there is an in app purchase which deletes adds that also uses that symbol but I do add a reminder at the the top this uses real money. Maybe in the future I could add a warning at the beginning of the claim to clarify that.

I appreciate you downloading the app and giving it a try!

### 4/5 — love the app! however…

*2023-02-16*

i’m a little torn on this. this is an incredibly well made game/app that is not only pretty fun but also looks really aesthetically pleasing. i’m a college student who hates studying, but desperately needs to get better at calculus. i was looking for something that would turn practicing calculus (and math in general) into something more fun. this app is pretty much exactly what i was looking for, which is why i came here to review it. that being said, i just looked over the description again and i just realized that the app store it says it collects location and user data? i assume that’s probably just due to the fact that it’s free, but i’m still a little concerned. i know all apps have some type of tracking so i shouldn’t care but i usually try to avoid ones with several types of data collected. i already love this app a lot so i’ll keep playing it anyways, but i am still a little concerned about it. i wish someone could respond and explain if i’m overthinking it lol. it might just be the fact that ads inherently have trackers on them regardless of the app so idk

**Developer response:** First off thank you for the response! I did try quite hard to hit the aesthetically pleasing mark. As for your privacy concerns. I totally understand, in fact for those reasons I wanted to keep the amount of data as minimal as possible. However, due to the way ads work they require tracking of user data (which apparently includes location). If it helps, the location it tracks is “coarse location” so it doesn’t have your exact location.

You can also turn off tracking in the settings >> one by one >> Allow Tracking (OFF)

To give you a brief run down of how the different data is used to hopefully clarify any anxiety:

Location: coarse location, used by google fire base and ads. I personally don’t use it anywhere in my code but I can see like what country’s are accessing the app, but not what account is in what country (kind of anonymous)

Usage data: I’m Google Firebase I can see analytics on how often and how long my app is played for but again I can’t specifically see how long a certain user is playing.

Identifiers: This is just the email that you input and I can look at this since it’s the user base but I CANNOT see your passwords.

Overall most of the data gather is used either as analytics/diagnostics on Google Firebase or in ads. But I personally do not do anything malicious with the data.

Again thank you for the reply and the concerns!

### 5/5 — Great math game, but I have two suggestions!

*2023-01-30*

Long story short, this is one of the best math games I have ever played. You wouldn’t think it would be fun; after all, the problems aren’t disguised at all. However, with the fact that there are “golden” problems that give you artifacts and that there’s a “money” counter that goes up as you solve, it always keeps you coming back for more. I also appreciate the “Battle” Mode. However, I have two suggestions: make the “average time taken on arithmetic/algebra/trig/differential problems” display a “rolling average,” which excludes earlier problems. For example, only consider the times of the last 250 problems or so for the average. Since the point of this app is to get faster and better, a rolling average makes sense since after solving enough problems, it won’t matter how fast or slow you are, your average won’t budge since there’s so much data. It would help measure improvement and trends, showing how far you’ve come instead of reminding you of the past. It would also help refine precision for the battle mode, making sure you’re always being challenged no matter how good you are since you first started. Also, I’m over halfway done with collecting all the artifacts, and it’s worrying me about what I’ll do once I’ve found them all. For me, a big part of the game is the constant waiting for a golden problem. So, instead of having to add more artifacts, why not allow for duplicates once you’ve found them all? These duplicates would show as a simple number in the bottom-left corner of the artifact tile, and every duplicate you get would “upgrade” the artifact, making it more powerful. The boost wouldn’t have to be too big, but it would keep the thrill of golden problems after getting all of the artifacts. (More artifacts would not go unappreciated though.) However, One By One is a great app for anyone looking for a fun and fast way to improve their math skills, and it has problems for all ages: for a five-year old practicing addition, a fourteen-year old brushing up on algebra, or for a high-school student studying for their Trig or differentials final.

**Developer response:** Wow. Thank you for such a heartfelt review. I am glad you enjoy the app. I completely agree with changing the average to be more recent. Additionally I think having the artifact upgrades could add another level to the game without too much complexity. I am currently taking a pause of updates but once I get back into I'll definitely add these.

### 5/5 — Awesome summer learning tool

*2022-08-04*

My child loves this “game “ and is keeping their skills sharp during the summer

### 5/5 — Five stars

*2022-04-16*

Best math app ever

### 5/5 — I LOVE THIS APP

*2022-02-10*

Saved my grade and is such a game changer!! Highly recommend this app

**Developer response:** Thank you! That is amazing to hear.

## Frequently asked questions about One By One

### What kind of math subjects does this app cover?

This app covers a range of math subjects including arithmetic, algebra, trigonometry, and calculus derivatives. It offers practice problems for basic calculations, solving equations, understanding trigonometric functions, and applying derivative rules.

### How does the leveling system work?

You progress through a leveling system from level 1 to 99 by solving math problems. For every ten levels you achieve, a new set of mathematical questions is unlocked, providing continuous learning and challenges.

### Is this app free to use?

The app is free to download and use, but it does offer in-app purchases and contains advertisements. These may include options for additional features or to enhance the user experience.

### What are the unique features of this math game?

The app features a distinct retro Unicode/ASCII art style with nostalgic background music and satisfying key clicks. It also includes a leveling system, leaderboards, achievements, collectible math artifacts with upgrades, and an AI battle mode for targeted practice.

### Who is the target audience for this math app?

The app is designed for middle and high school students who want to improve their mental math skills. It's suitable for those needing to practice foundational arithmetic, tackle algebra, master trigonometry, or understand calculus derivatives.

## Version history (last 5 releases)

### 1.9.0 — 2026-09-01

Massive Retro Overhaul & Supporter Update!

We’ve completely rebuilt One By One from the ground up for a smoother, more tactile math experience. Here is what’s new in this version:

UI & Aesthetic Overhaul
Tactile Mechanical Keys: Flat sprites are out. Enjoy a responsive native layout with traveling keycaps, haptic clicks, and zero-blur drop shadows.  

Dynamic LCD Screen: A true-to-life LCD print head now amends text character-by-character as you solve instead of just refreshing.  

Polished ASCII Graphics: Redesigned unit circles, level badges, and progress bars match the new physical grid perfectly.  

New Supporter License & Themes
Premium Themes: Supporters can now swap the classic cream design for new terminal themes: Phosphor (Green CRT), Amber (Gas-plasma), and Papertape (Teletype).  

Cash Multiplier: The Supporter License also grants a permanent 1.25x practice cash bonus.  

Sandbox Mode & Advanced Stats
Sandbox Mode: Experiment and practice specific problem types at your own pace without pressure.  

Live Balance Graph: Track your recent earnings with a dynamic ASCII plot covering your last 30 minutes of gameplay.  

Speed Tracking: Watch your mental math improve with real-time average seconds-to-solve tracking.  

Math Engine Improvements & Bug Fixes
Crash-Proof Parsing: The answer checker now safely handles malformed inputs and typos without throwing errors.  

Calculus Fixes: The derivative generator is smarter and will no longer ask for derivatives at undefined or impossible points.  

Algebra & Trig Fixes: Restored previously "hidden" equation shapes (like x-a=b) to your runs, and fixed the mathematical ranges for inverse cot problems.

### 1.7.0 — 2022-08-15

Scaring bugs away so you can keep mathing.

### 1.6.0 — 2022-01-20

You can now purchase premium mode which includes no ads and a permanent x1.5 multiplier on the Battles mode.
In Battles, there's now a pause between problems.

### 1.5.7 — 2022-01-07

- Fixed an issue with displaying skips.

### 1.5.6 — 2022-01-06

- Some minor performance updates
- Allowed to play before making an account
- Allowed for deleting accounts

## Apps similar to One By One

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Mathscapes: Math Brain Algebra](https://appshunter.io/ios/app/mathscapes-math-brain-algebra/id1490675627) | 4.8 (756) | Free | Games |
| [Algebra Game with Equations](https://appshunter.io/ios/app/algebra-game-with-equations/id904192350) | 3.9 (821) | Free | Games |

## More apps by Brice Brown

- [Atomic Amasser \| Idle Sim](https://appshunter.io/ios/app/atomic-amasser-idle-sim/id1634962166)
- [Neptune: Navigation Rules](https://appshunter.io/ios/app/neptune-navigation-rules/id6756641315)
- [Space Inspector](https://appshunter.io/ios/app/space-inspector/id6783617599)

All apps by Brice Brown: https://appshunter.io/developer/1555846025

## Related topics

[hands on equations](https://appshunter.io/ios/topics/hands-on-equations)

---

*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 2026-09-09.*