<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8">
<title>カウントダウンゲーム</title>
<style>
.box {
width: 50px;
height: 50px;
margin: 10px;
background-color: lightblue;
display: inline-block;
text-align: center;
line-height: 50px;
font-size: 20px;
}
#infobox {
margin-top: 20px;
font-size: 24px;
}
</style>
</head>
<body>
<h1>3秒以内に「当たり」を見つけよう!</h1>
<div id="game">
<div class="box">1</div>
<div class="box">2</div>
<div class="box">3</div>
<div class="box">4</div>
<div class="box">5</div>
<div class="box">6</div>
<div class="box">7</div>
<div class="box">8</div>
<div class="box">9</div>
<div class="box">10</div>
</div>
<button id="startButton">スタート</button>
</body>
</html>