index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="css/styles.css">
    <link rel="stylesheet" href="https://necolas.github.io/normalize.css/8.0.1/normalize.css">
    <title>Encriptador de texto</title>
</head>
<body>
    <div class="contenido">
        <div class="alerta"></div>
        <div class="contenedor">
            <form class="formulario">
                <textarea name="texto" id="texto" placeholder="Introduce tu texto"></textarea>
                <div class="botones">
                    <button class="boton btn1">Encriptar</button>
                    <button class="boton btn2">Desncriptar</button>
                </div>
            </form>

            <div class="encriptado">
                <textarea class="textarea" ></textarea>
                <button class="boton btn">Copiar</button>
            </div>
            
        </div>
    </div>
    <script src="js/app.js" type="module"></script>
</body>
</html>