Neumorphism Calculator
Try the Live Calculator · Screenshots · Features · Getting started
A calculator with a soft neumorphic interface, written in strict TypeScript with no UI framework. It offers two calculators in one page: a NORMAL calculator that evaluates left to right like a classic pocket calculator, and a PRO calculator with real operator precedence, parentheses, squares and square roots. Both show the result live while you type, and both are fully usable from the mouse or the keyboard.
The project is built as an exercise in clean, testable design: calculation logic is completely separate from the DOM, and the whole thing is covered by an automated test suite.
Live demo
Hosted on Vercel. Switch between NORMAL and PRO, and between LIGHT and DARK, with the two toggles above the calculator; your choice is remembered on that device.
Screenshots
Real screenshots of the running app. The large display shows the live result before = is pressed.
| LIGHT | DARK |
|---|
NORMAL2 + 3 × 4 → 20 (left to right) | | |
PRO2 + 3 × (4 + √16) → 26 (precedence, parentheses, √) | | |
Features
Two calculators
- NORMAL evaluates strictly left to right:
2 + 3 × 4 = 20.
- PRO follows mathematical operator precedence:
2 + 3 × 4 = 14.
- Live result preview in both modes: type
5 + 2 and the large display already shows 7, with no = needed. While you type a single number it is shown exactly as typed (5., 0.50). An unfinished expression (5 +, (5 + 3) keeps showing the last valid value instead of an early error.
- Expression line above the result shows what was entered (
2 + 3 × 4, and 2 + 3 × 4 = once finished). Long expressions scroll and keep the newest part in view.
- Each calculator keeps its own state when you switch between them.
PRO extras
- Parentheses, including nested ones:
((1 + 2) × (3 + 4)) = 21.
- Square (
x²) and square root (√).
- Unary minus, including before a group:
5 × -(2 + 3) = -25.
- Implicit multiplication is made visible:
2(3) becomes 2 × (3).
- Open groups and unfinished input are reported as an
Error when you press =, never silently repaired.
Shared behavior
-
Digits, decimal point, + − × ÷, AC, +/- and % with contextual percentage rules:
| Keys | Result |
|---|
50 % | 0.5 |
200 + 10 % = | 220 |
200 - 10 % = | 180 |
200 × 10 % = | 20 |
200 ÷ 10 % = | 2000 |
-
Numbers are limited to 15 digits. Values keep full precision internally and are rounded only for display, so 0.1 + 0.2 = 0.3. Integers are exact up to 2^53; larger results use exponent notation (for example 9.999999998e+19).
-
Division by zero, √ of a negative number and overflow show Error; the next digit or AC recovers.
Interface
- LIGHT and DARK themes, switched independently of NORMAL/PRO with two toggles above the calculator, with smooth transitions.
- The chosen calculator mode and theme are remembered in
localStorage (only these two preferences are stored, never the calculation). Invalid or unavailable storage falls back to the defaults. A saved dark theme or PRO mode is applied before the first paint to avoid a flash of the wrong look.
- The large display shrinks its font so long values stay inside it. The layout is fluid and has been checked from about 272 px wide up to desktop widths.
Keyboard input
| Key | Action |
|---|
0–9, . | Digits and decimal point |
+ - * / | Operators (- also starts a negative number in PRO) |
Enter or = | Equals |
Escape | AC |
% | Percent |
( ) | Parentheses (PRO only) |
Keys are ignored while typing in a text field and when Ctrl, Cmd or Alt is held, so browser shortcuts keep working. There are no keyboard shortcuts for x² and √.
Tech stack
Taken from package.json; there are no runtime dependencies.
- TypeScript 7 in
strict mode, with unused locals and parameters treated as errors
- HTML and CSS (CSS custom properties drive both themes)
- Vite 8 for development and production builds
- Vitest 5 with jsdom for tests
Architecture
Calculation code never touches the DOM. Rendering, input handling, settings and calculation each live in their own small classes, wired together in one place.
src/
├── main.ts # entry point
├── calculator/ # calculation logic (no DOM)
│ ├── BasicCalculator.ts # interface both calculators implement
│ ├── CalculatorEngine.ts # NORMAL rules as state transitions
│ ├── CalculatorState.ts # typed state model and display/preview text
│ ├── NormalCalculator.ts # engine + the expression entered on it
│ ├── Operator.ts, NumberEntry.ts, NumberFormatter.ts
│ └── pro/ # PRO: tokens, evaluator, formatter, calculator
├── classes/ # CalculatorApp (composition root), InputHandler
├── ui/ # CalculatorUI (rendering), DisplayFitter
├── settings/ # CalculatorModeSetting, PreferenceStore, UserPreferences
├── themes/ # ThemeManager
└── styles/style.css # layout and both themes
| Class | Responsibility |
|---|
CalculatorApp | Composition root. Connects input, the active calculator, the UI, the settings and the saved preferences, and owns the start/dispose lifecycle. |
BasicCalculator | The interface (displayValue, expressionText, digits, operators, =, AC…) that lets the app drive either calculator the same way. |
CalculatorEngine, CalculatorState | NORMAL rules as transitions between typed states (entering, awaitingOperand, result, error), including the left-to-right live preview. |
NormalCalculator | Wraps the engine and records the expression for display. It never calculates by itself. |
ProCalculator | Turns key presses into expression tokens and refuses key presses that would build a malformed expression. |
ExpressionEvaluator | A pure recursive-descent parser for PRO expressions (precedence, parentheses, x², √, unary minus). No eval. |
ExpressionFormatter | Turns tokens into the expression text. |
Operator, NumberEntry, NumberFormatter | Shared operator table and percent rule, number typing rules, and display formatting. |
InputHandler | Converts clicks and key presses into typed callbacks; removes all its listeners in dispose(). |
CalculatorUI, DisplayFitter | Render the display, expression line and toggles; shrink the font only when text overflows. |
CalculatorModeSetting, ThemeManager | The two independent settings. Neither knows about the other. |
PreferenceStore, UserPreferences | Safe localStorage access and the two typed, validated preferences. |
Engineering principles in the code
- Separation of concerns: math lives in
calculator/, rendering in CalculatorUI, events in InputHandler, persistence in settings/. The mode and theme settings are separate classes, and tests check that they import nothing and know nothing of each other.
- Single responsibility: each class above has one job, for example
NormalCalculator only tracks the expression and leaves every number to CalculatorEngine.
- Dependency injection and polymorphism:
CalculatorApp, ProCalculator, ThemeManager and CalculatorModeSetting receive their collaborators or initial values through constructors (with defaults), and the app uses NORMAL and PRO interchangeably through BasicCalculator. This is what makes the unit tests easy to write.
- DRY: both calculators share
Operator.calculate, the percent rule, number entry rules, number formatting and operator symbols instead of duplicating them.
- KISS: no framework and no
eval; a short recursive-descent parser, and previews are computed from existing state without a second evaluator.
- Clean code and strictness: strict TypeScript, discriminated unions for states and tokens, immutable state objects, read-only preview getters that never mutate state, and descriptive comments that explain intent.
Not every SOLID principle is demonstrated formally; the points above are the ones the code actually shows.
Getting started
Requirements: Node.js 22.13 or newer (as required by the current Vite, Vitest and jsdom versions) and npm.
git clone https://github.com/TamarMosheev/Neumorphism-Calculator-.git
cd Neumorphism-Calculator-
npm install
npm run dev
Vite prints the local address (by default http://localhost:5173/); open it in your browser.
npm run build # type-check with tsc, then build to dist/
npm run preview # serve the production build locally
npm test # run the whole test suite once
npx tsc --noEmit # type-check only
Testing
npm test runs the suite once with Vitest. At the time of writing, 1579 tests in 30 files pass. They cover:
- unit tests for the engine, state model, operators and number formatting;
- the PRO parser, formatter and calculator, including precedence, parentheses, unary minus, percentages, incomplete input and errors, plus randomized "never throws" checks;
- live preview behavior in both modes, and keyboard handling including cleanup of listeners;
- DOM tests, run in jsdom against the real
index.html, that click the actual buttons and check the display and expression line;
- preference persistence across simulated reloads, including invalid and unavailable storage;
- theme switching and that both themes define the same CSS variables.
Tests live next to the code they cover, in *.test.ts files.
Status
Version 0.1.0. Both calculators, both themes, persistence and keyboard input are working. A live demo and screenshots are available above. No license has been specified.
