A lightweight, vanilla‑JavaScript calculator that runs entirely in the browser. SimpleCalc provides the essential arithmetic operations with an intuitive button layout, keyboard shortcuts, and graceful error handling – all without any build steps or external dependencies.

• HTML5 – Semantic markup for the calculator UI.
• CSS3 – Flexbox layout, responsive design, and visual styling.
• JavaScript (ES2021) – Core logic for expression evaluation, event handling, and keyboard support.

• Basic arithmetic: addition, subtraction, multiplication, division.
• Decimal numbers and chaining of operations.
• Clear (C) and backspace (⌫) functionality.
• Percentage (%) handling (interpreted as /100).
• Sign toggle (±) for the current number.
• Keyboard shortcuts for all buttons (e.g., 1‑9, 0, +, -, *, /, Enter for =).
• Real‑time display of the current expression and result.
• Graceful handling of division by zero and malformed expressions with user‑friendly error messages.
• Responsive layout that works on desktop and mobile browsers.

1. Clone the repository

   git clone <repository-url>
   cd SimpleCalculator

2. Open the app
   • Double‑click index.html or open it in any modern browser (Chrome, Firefox, Edge, Safari, etc.).
   • No build step, server, or package manager is required – the app is pure client‑side.

┌─────┬─────┬─────┬─────┐
│  C  │  ⌫  │  %  │  ÷  │
├─────┼─────┼─────┼─────┤
│  7  │  8  │  9  │  ×  │
├─────┼─────┼─────┼─────┤
│  4  │  5  │  6  │  -  │
├─────┼─────┼─────┼─────┤
│  1  │  2  │  3  │  +  │
├─────┼─────┼─────┼─────┤
│  ±  │  0  │  .  │  =  │
└─────┴─────┴─────┴─────┘

• C – Clear the entire expression.
• ⌫ – Delete the last character (backspace).
• % – Percentage (interpreted as /100).
• ÷, ×, -, + – Arithmetic operators.
• ± – Toggle sign of the current number.
• . – Decimal point.
• = – Evaluate the expression.

• Error: Division by zero – Shown when the expression attempts to divide by zero.
• Error: Invalid expression – Shown for malformed input (e.g., two operators in a row).
• Errors replace the result display until the user clears or edits the expression.

The calculator uses a flexible Flexbox grid and media queries to adapt to different screen sizes. On mobile devices the buttons and display scale down while remaining easily tappable, ensuring a smooth experience on both portrait and landscape orientations.

Contributions are welcome! Feel free to open issues or submit pull requests.

1. Fork the repository.
2. Create a feature branch (git checkout -b feature/awesome‑feature).
3. Make your changes, ensuring the calculator still works by opening index.html.
4. Commit with a clear message and push to your fork.
5. Open a pull request against the main branch.

Please keep the code style consistent (ES2021, 2‑space indentation) and avoid adding external dependencies.

This project is licensed under the MIT License – see the LICENSE file for details.