# Arity One — Easy sketch app

> Easy sketch app (iPhone/iPad app by Kiet Nguyen Tuan.)

- Source: https://appshunter.io/ios/app/arity-one/id6811904532 (this page in markdown: same URL + `.md`)
- Developer: [Kiet Nguyen Tuan](https://appshunter.io/developer/1647733663)
- Category: Productivity, Developer Tools
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 16.0 · 21 MB
- Languages: American English
- Released: 2026-09-21
- Data updated: 2026-09-26
- User reviews in markdown: https://appshunter.io/ios/app/arity-one/id6811904532/reviews.md

## What is Arity One?

Arity opens and you draw. No account, no manual, no setup screen.

Pick a diagram type and sketch the way you would on paper. Each type already knows its own notation, so you never have to remember which shape means what or which arrow is allowed where. Arity handles that. You handle the thinking.

FIVE DIAGRAM TYPES

• Freestyle: a blank canvas, no rules.
• Flow chart: Terminal, Process, Decision, I/O, Connector. Break a rule and it says so: only Decision and Connector may branch.
• Class diagram: class, abstract, interface; fields and methods; association, aggregation, composition, inheritance, implementation, with multiplicities. Checked against OOP: missing abstract methods, inheritance cycles, interfaces used wrongly.
• ER: both crow's foot and Chen, one button apart.
• Mind map - official style: one central idea, organic tapering branches, one keyword each, colour inherited down the branch.

The diagram argues back when the thinking is wrong. That is the difference between a drawing tool and a thinking tool.

APPLE PENCIL

Strokes follow your pressure, smooth down to every sampled point. Rest your whole palm on the glass and keep drawing. Two fingers pan and zoom; a second finger undoes whatever the first one just started, so you never nudge a shape by accident. Press and hold stands in for a right click. No Pencil? A finger draws just as well - and Settings lets you decide whether a finger should draw or move the canvas.

ONE PROJECT, ONE FILE

A whole project lives in a single document with its own folders inside it. It sits in Files under On My iPad › Arity, so backing it up, sending it on, or opening it from iCloud Drive works like any other document. Every change saves itself after a second or so, when you switch diagrams, and when the app goes to the background - written to a temporary file and renamed, so a half-written project is not a thing that can happen.

PRESENT ON AN EXTERNAL DISPLAY

Plug in a screen and the Present button appears. The external display shows only the diagram while your iPad keeps its toolbar and panels. Not mirroring.

ALSO

• Arrows bind to shapes and follow them as they move or resize.
• Combine shapes with union, intersect, subtract and exclude.
• Export PNG from 1x to 4x, transparent or on a colour you choose.
• Library: save a selection as an asset and drag it back out later.
• Notes, images, groups, undo/redo, minimap.
• The entire app is under 5 MB.

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Arity One Lifetime | $29.99 | one-time |



## Version history (last 1 release)

### 1.0 — 2026-09-21

No release notes.

## More apps by Kiet Nguyen Tuan

- [Mino](https://appshunter.io/ios/app/mino/id6443619224)
- [Greeny](https://appshunter.io/ios/app/greeny/id6444045110)
- [Dev Pass](https://appshunter.io/ios/app/dev-pass/id6708239668)
- [Aviec - Hire and Find Jobs](https://appshunter.io/ios/app/aviec-hire-and-find-jobs/id6738648380)
- [Hatomic](https://appshunter.io/ios/app/hatomic/id6738987299)
- [Alife - A Balance Life](https://appshunter.io/ios/app/alife-a-balance-life/id6739061702)

All apps by Kiet Nguyen Tuan: https://appshunter.io/developer/1647733663

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*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 2026-09-26.*