index.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="css/style.css">
    <title>Simon Dice</title>
</head>
<body>
<div class="gameboard">
    <div id="celeste" class="color celeste left" data-color="celeste"></div>
    <div id="violeta" class="color violeta right" data-color="violeta"></div>
    <div id="naranja" class="color naranja left" data-color="naranja"></div>
    <div id="verde" class="color verde right" data-color="verde"></div>
    <button id="btnEmpezar" class="btn-start" onclick="empezarJuego()">Empezar a jugar!</button>
</div>

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        crossorigin="anonymous" referrerpolicy="no-referrer"></script>

<script src="js/app.js"></script>
</body>
</html>