Residue: Mathematics
Proofs, puzzles, number theory
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
Problems made fresh on your phone and checked before you see them. Colour a Ramsey board, find the false step in a proof, keep a Daily streak.
Residue is mathematics you do, not read. Every problem is generated on your device and checked before you see it, and one you have solved is not served to you again.
FOUR WAYS TO PLAY
• Crucible: modular powers, Diophantine equations, power sums, counting, inequalities, geometry, polynomials, trigonometry and linear algebra, at a tier that follows your recent results. Sprint puts it against the clock, with a countdown on the Lock Screen.
• Chromatic Ramsey: colour every edge of a complete graph without making a forbidden shape in one colour. Hints name an edge and the reason for its colour. Two boards cannot be won, and finding out why is the lesson.
• Spoof Hunt: a derivation reaches something false. Exactly one step is illegal. Find it.
• Daily Conundrum: one problem a day, the same on every device, with a streak to keep.
ANSWERS, NOT GUESSES
• No multiple choice. Answer on the pad the problem needs: a whole number, a fraction, a root or a multiple of π. Grading is exact.
• Stuck? A lemma reveals the next rung of the argument, not the answer. Once you solve, the whole ladder is yours.
• Work it out on the scratchpad. Circle your answer and it goes into the pad for you to check.
• Geometry problems draw their figure, and can show a helpful construction.
THEOREMS
Sixteen theorems behind the problems, from Euclid's primes to Ptolemy and the roots of unity, each with a proof, a step by step ladder and a sandbox to play in. Search them by what they are about.
EVERYWHERE
• Export a solved problem and its ladder as a PDF or a LaTeX file.
• Widgets for the Home Screen, the Lock Screen and iPad.
• An Apple Watch drill answered with the Digital Crown, and complications for your rating and your streak.
• Your Daily record and progress follow you across devices through iCloud.
• In English and Japanese. VoiceOver reads every problem.
FREE, WITH PLANS
Residue is free with ads, and three free lemmas a day; a short video buys one more. Two optional subscriptions, in one group:
• Ad-Free (yearly) removes the ads and keeps the three free lemmas a day.
• Residue Plus (monthly or yearly) removes the ads, makes lemmas unlimited, opens every theorem and exports clean copies.
Prices are shown in the app before you buy. Subscriptions renew automatically unless cancelled at least 24 hours before the end of the period, and are managed in your App Store account settings.
Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Terms: https://marsstudio.app/residue/terms
Privacy Policy: https://marsstudio.app/residue/privacy
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
The developer, Atchutarao Killamsetty, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Used to Track You
The following data may be used to track you across apps and websites owned by other companies:
- Identifiers
Data Linked to You
The following data may be collected and linked to your identity:
- Location
- Identifiers
- Usage Data
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Diagnostics
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Atchutarao Killamsetty
- Size
- 23.7 MB
- Category
- Education
- Compatibility
Requires iOS 27.0 or later.
- iPhone
Requires iOS 27.0 or later. - iPad
Requires iPadOS 27.0 or later. - Mac
Requires macOS 27.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 27.0 or later. - Apple Watch
Requires watchOS 11.0 or later.
- iPhone
- Languages
- English and Japanese
- Age Rating
13+
- 13+
- Contains
Advertising
- In-App Purchases
Yes
- Ad-Free Yearly $2.99
- Residue Plus Monthly $1.99
- Residue Plus Annual $9.99
- Copyright
- © 2026 MARS Studio
