index.html

<!DOCTYPE html>
<html lang="br-pt">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="css/estilo.css">
    <title>Calculadora Básica</title>
</head>
<body>
    <h1>Calculadora Basica</h1>
    <div id="btn-add">
        <input id="valor1" type="text" placeholder="Digite um numero"><br>
        <input id="valor2" type="text" placeholder="Digite um numero">        
    </div>
    <div class="btn-teste">
        <button id="soma" onclick="soma()">+</button>    
        <button id="substracao" onclick="substracao()">-</button>
        <button id="multiplica" onclick="multiplica()">*</button>
        <button id= "divisao" onclick="divide()">/</button>
        <button id="soma" onclick="porcento()">%</button>    
        <button id="substracao" onclick="valorPi()">π</button>
        <button id="multiplica" onclick="factorial()">x!</button>
        <button id= "divisao" onclick="divideInt()">DIV</button>
    </div>
    <div class="resultado">
        <input  type="text" name="" id="total">
    </div>
    

    <!--Arquivos JS-->
    <script src="js/base.js"></script>
</body>
</html>