<html>

<head>

    <meta charset="utf-8">

    <meta http-equiv="X-UA-Compatible" content="IE=edge">

    <meta name="viewport" content="width=device-width,initial-scale=1">



    <title>Rotary Calculator</title>

    <meta name="description" content="A calculator app with an old rotating number entering system like telephones">

    <meta name="keywords" content="rotary calculator, old calculator, number entering system">



    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>

    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet"

        integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous">

    <link href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet">

    <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet">



    <script type="text/javascript">

        try {

            // App Javascript Goes Here. Place your entire script content inside the try block for error handling.

            document.addEventListener("DOMContentLoaded", function() {

                // Function to handle rotary number input

                function handleNumberInput(number) {

                    var display = document.getElementById("display");

                    display.value += number;

                }

                

                // Function to clear the display

                function clearDisplay() {

                    var display = document.getElementById("display");

                    display.value = "";

                }

                

                // Function to calculate the result

                function calculateResult() {

                    var display = document.getElementById("display");

                    var expression = display.value;

                    

                    try {

                        var result = eval(expression);

                        display.value = result;

                    } catch (error) {

                        display.value = "Error";

                    }

                }

                

                // Attach event listeners to the number buttons

                var numberButtons = document.getElementsByClassName("number-button");

                for (var i = 0; i < numberButtons.length; i++) {

                    numberButtons[i].addEventListener("click", function() {

                        var number = this.getAttribute("data-number");

                        handleNumberInput(number);

                    });

                }

                

                // Attach event listener to the clear button

                var clearButton = document.getElementById("clear-button");

                clearButton.addEventListener("click", clearDisplay);

                

                // Attach event listener to the calculate button

                var calculateButton = document.getElementById("calculate-button");

                calculateButton.addEventListener("click", calculateResult);

            });



        } catch (error) {

             // This will throw the error to the parent window.

            throw error;

        }

    </script>

    

    <style>

        /* App CSS Goes Here */

        body {

            font-family: 'Roboto', sans-serif;

            background-color: #f2f2f2;

        }

        

        .container {

            max-width: 400px;

            margin: 0 auto;

            padding: 20px;

            background-color: #fff;

            border-radius: 10px;

            box-shadow: 0px 0px 10px rgba(0,0,0,0.1);

        }

        

        .calculator {

            display: flex;

            flex-wrap: wrap;

            justify-content: space-between;

        }

        

        .calculator button {

            width: 30%;

            height: 60px;

            margin-bottom: 10px;

            font-size: 20px;

            color: #fff;

            background-color: #4CAF50;

            border: none;

            border-radius: 5px;

            cursor: pointer;

        }

        

        .calculator button:hover {

            background-color: #45a049;

        }

        

        .calculator button:active {

            background-color: #3e8e41;

        }

        

        .display {

            width: 100%;

            height: 60px;

            margin-bottom: 10px;

            padding: 10px;

            font-size: 24px;

            color: #333;

            background-color: #f2f2f2;

            border: none;

            border-radius: 5px;

            text-align: right;

        }

    </style>

</head>

<body>

    <div id="main-container" class="container">

        <h1>Rotary Calculator</h1>

        <div class="calculator">

            <input id="display" class="display" type="text" readonly>

            <button class="number-button" data-number="1">1</button>

            <button class="number-button" data-number="2">2</button>

            <button class="number-button" data-number="3">3</button>

            <button class="number-button" data-number="4">4</button>

            <button class="number-button" data-number="5">5</button>

            <button class="number-button" data-number="6">6</button>

            <button class="number-button" data-number="7">7</button>

            <button class="number-button" data-number="8">8</button>

            <button class="number-button" data-number="9">9</button>

            <button class="number-button" data-number="0">0</button>

            <button id="clear-button">Clear</button>

            <button id="calculate-button">Calculate</button>

        </div>

    </div>

</body>

</html>