PopCalc
Math, but make it physical.
PopCalc is an Android calculator with sculpted 3D numerals, tactile haptics, musical sound effects, hand-crafted skins, materials, two limited-edition drops with hidden scenes, a live currency converter and one secret skin you have to earn.
- Version: 1.6.0
- Platform: Android
- Built with: Flutter
- Works 100% offline, no ads, no account, zero data collected (go online only if you want live currency rates)
Demo
Screenshots
Features
3D numerals and motion
- Extruded 3D numerals with bevelled edges, soft shadows and a subtle grain texture
- Tilt the phone or drag the number to shift it in 3D
- Each new digit turns into place as you type, with no jumping around
- A speed-line burst when the answer lands
Haptics
- Native Android haptics with a different feel for each key type
- Heavier feedback on errors
- Adjustable haptic strength
Sound
- Three sound packs: Pop, Mellow and Typewriter
- Number keys play a pentatonic melody as you type
- Sound only where it matters; everything else is haptics
- Plays alongside your music without pausing it
Math
- Exact decimal arithmetic, so
0.1 + 0.2 = 0.3
- Live preview of the answer while you type
- Tap any number or operator in the expression to edit it, and the answer updates instantly; backspace trims a selected number one digit at a time
- Big powers stay fast, so compound interest like
(1 + 0.055 ÷ 365)^365 answers instantly
- History restores the full expression so you can keep editing
Scientific & Converter
- One switch in Settings adds two buttons to the top bar
- Scientific: powers, roots, brackets, trig (DEG/RAD), logs, π, e and factorial, in a tray that folds away. Switch between simple and scientific with one tap
- Currency converter: 33 currencies, first in the converter. Works offline with rates built into the app; tap the rates pill to fetch today's rates from the internet whenever you like. Flags, currency signs, money-style rounding
- Unit converter: ten more categories with exact factors, on its own screen. Swipe through units and categories like a slider. Data units show both families side by side: decimal (1 GB = 1000 MB) and binary (1 GiB = 1024 MiB), plus bits for internet speeds
Quick Settings tile
- Add a PopCalc tile to the pull-down Quick Settings panel (Settings → Quick Settings Tile) and open the calculator from anywhere with one tap
Make it yours
- Eight home-screen icons to choose from in Settings, free for everyone (the official logo stays the default)
- A secret skin, Newsprint, earned by cracking the editor's confidential case: five riddles, each hiding somewhere in the app. Tap the ??? skin in Settings to open the file
- Errors are written as jokes, with the plain reason underneath. Results too big to show get a "that's what she said" all of their own
Privacy and performance
- Works fully offline; nothing you type ever leaves your phone. The only optional online feature is fetching live currency rates, and it sends nothing about you
- No ads, no account, no data collected
- Lite Effects mode for low-end devices
Skins
Each skin restyles the whole app: numerals, keys, sheets, celebration and status bar.
| Skin | Style | Background | Accent | Tier |
|---|
| Charcoal | Dark, white numerals, amber operators | #141414 | #FFA000 | Free |
| Marigold | Sunny gold and vermilion | #FFAE00 | #D61800 | Free |
| Blueprint | Cyanotype paper, hollow line-drawn numerals | #0B3C8C | #FFD23F | Free |
| Matcha | Sage paper, ink and terracotta | #DDE4D0 | #A8431F | Pro |
| Frost | Nordic ice, navy numerals | #E8EFF5 | #BF360C | Pro |
| Velvet | Deep wine, cream and rose gold | #3A0A1B | #E8A87C | Pro |
Limited drops (until 11 January 2027): Mirage, living dunes under a sky that follows your clock, and Reckoning, a doomsday clock on your phone's own time. Each has its own film-style sounds, haptics and a hidden scene to find. $2.99 each or both in the Dunesday bundle for $4.99; yours for good once bought.
Pro skins and the five materials (Chrome, Glass, Wood, Neon, Mechanical: a look with its own sound and haptics) are one-time purchases through Google Play, singly or all together in the Everything bundle. Nothing needed to do math will ever be locked.
Get it
PopCalc is on Google Play: https://play.google.com/store/apps/details?id=com.ornobaadi.popcalc
Feedback and feature ideas are welcome in Issues.
How the math works
Order of operations
Multiply and divide come before add and subtract. Operations at the same level run left to right.
1 + 2 × 3 → 7
8 ÷ 4 + 2 → 4
Percent
| Input | Meaning | Example | Result |
|---|
a + b% | a + (a × b / 100) | 1024 + 5% | 1075.2 |
a − b% | a − (a × b / 100) | 200 − 15% | 170 |
a × b% | a × (b / 100) | 80 × 25% | 20 |
a ÷ b% | a ÷ (b / 100) | 50 ÷ 25% | 200 |
b% | b / 100 | 12% | 0.12 |
a% ± b% | percentages add | 50% + 10% | 0.6 |
Edge cases
| Case | Behaviour |
|---|
| Divide by zero | Shows a joke ("CAN'T DIVIDE BY ZERO" and friends) with the plain reason underneath; the expression stays editable |
| Consecutive operators | The latest operator replaces the previous one |
| Leading zeros | 007 becomes 7 |
| Very large results | Scientific notation beyond 15 significant digits |
| Trailing zeros | 2.50 shows as 2.5 |
Repeated = | Ignored, so no duplicate history entries |
Project structure
lib/
├── core/
│ ├── engine/ # Pure-Dart math: Expression, Parser, Evaluator, Formatter
│ ├── app_icon/ # Home-screen icon choices (Android launcher aliases)
│ ├── audio/ # Sound packs (flutter_soloud)
│ ├── haptics/ # Native Android haptics via MethodChannel
│ ├── storage/ # Settings and history
│ └── theme/ # Skin colour tokens
└── features/
├── calculator/ # Controller, 3D numeral painter, keypad, animations
├── history/ # History sheet
├── settings/ # Skin picker and preferences
└── splash/
- State management: Riverpod
- Math:
decimal package, with no Flutter imports in the engine
- Sounds are generated by
tool/generate_sounds.py
- Alternate launcher icons are generated by
tool/generate_app_icons.py
Build from source
flutter pub get
flutter test
flutter run
Release builds:
flutter build appbundle --release
flutter build apk --release
Platform
| |
|---|
| Android | Supported |
| iOS | Planned |
| Orientation | Portrait (scientific mode can rotate to landscape) |
| Network | None |
| Data collected | None (privacy policy) |
License
- App source: MIT
- Fonts: Antonio and Bebas Neue, SIL Open Font License (Antonio licence)
- Sounds: procedurally generated, original to PopCalc
PopCalc is not affiliated with Google, Apple or Casio.
