let display = document.getElementById('display');  
let currentInput = '';  
let previousInput = '';  
let operation = null;  
  
function appendNumber(number) {  
    currentInput += number;  
    display.textContent = currentInput;  
}  
  
function appendDecimal(dot) {  
    if (!currentInput.includes(dot)) {  
        currentInput += dot;  
        display.textContent = currentInput;  
    }  
}  
  
function chooseOperation(op) {  
    if (currentInput === '') return;  
    if (previousInput !== '') {  
        calculateResult();  
    }  
    operation = op;  
    previousInput = parseFloat(currentInput);  
    currentInput = '';  
}  
  
function clearDisplay(clear) {  
    if (clear === 'C') {  
        display.textContent = '0';  
        currentInput = '';  
        previousInput = '';  
        operation = null;  
    } else if (clear === 'AC') {  
        // Full reset (not implemented in basic example)  
    }  
}  
  
function calculateResult(equals) {  
    let result;  
    const prev = previousInput;  
    const curr = parseFloat(currentInput);  
    if (isNaN(prev) || isNaN(curr)) return;  
      
    switch (operation) {  
        case '+':  
            result = prev + curr;  
            break;  
        case '-':  
            result = prev - curr;  
            break;  
        case '*':  
            result = prev * curr;  
            break;  
        case '/':  
            result = prev / curr;  
            break;  
        case '%':  
            result = prev % curr;  
            break;  
        default:  
            return;  
    }  
    display.textContent = result;  
    previousInput = result;  
    currentInput = '';  
    operation = null;  
}  
  
// Bind equals button to calculate result  
document.querySelector('button[onclick="calculateResult(\'=\')"]').addEventListener('click', calculateResult);