text: const $buttons = document.querySelector('.buttons');
  const $resultContainer = document.querySelector('.result-container');
  let firstValue = '';
  let secondValue = '';
  let operator = '';
  let result = 0;
  let isOperator = false;
  
  $buttons.addEventListener('click', (event) => {
    const $btn = event.target;
    const isNumber = $btn.classList.contains('number');
    isOperator = $btn.classList.contains('operator');
    const value = $btn.innerHTML;
    const id = $btn.id;
  
    if (isNumber && !operator) {
      firstValue += value;
      result = firstValue;
    } else if (isOperator) {
      operator = value;
    } else {
      secondValue += value;
      result = secondValue
    }
    if($btn.classList.contains('equal')) {
      switch(operator) {
        case '+': 
          firstValue = parseFloat(firstValue);
          secondValue = parseFloat(secondValue);
          result = firstValue + secondValue;
        break;
        case '-': 
          firstValue = parseFloat(firstValue);
          secondValue = parseFloat(secondValue);
          result = firstValue - secondValue;
        break;
        case '/': 
          firstValue = parseFloat(firstValue);
          secondValue = parseFloat(secondValue);
          result = firstValue / secondValue;
        break;
        case '*': 
          firstValue = parseFloat(firstValue);
          secondValue = parseFloat(secondValue);
          result = firstValue * secondValue;
        break;
      }
  
    } if($btn.classList.contains('AC')) {
      firstValue = "";
      secondValue = 0;
      operator = "";
      result = 0;
    }
  
    $resultContainer.innerHTML = result;
  })