使用HTML+JavaScript实现扫雷小游戏

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>SaoLei</title>
<style type="text/css">
table
{
    
    
-webkit-touch-callout: none; /* iOS Safari */

-webkit-user-select: none; /* Chrome/Safari/Opera */

-khtml-user-select: none; /* Konqueror */

-moz-user-select: none; /* Firefox */

-ms-user-select: none; /* Internet Explorer/Edge */

user-select: none; /* Non-prefixed version, currently not supported by any browser */
}
</style>
</head>

<body>
<center style="margin:150px auto;">
<h2 style="font-family:Comic Sans Ms;">Mine Clearance（扫雷）&diams;</h2>
<p>请设置行和列开始游戏</p>
<p>游戏难度：<select id="level" onchange="changelevel()"><option>小白级</option><option>大神级</option></select></p>
<p id="select_level"></p>
行:  <input type="text" id="rows"> 
列: <input type="text" id="cols"> 
<button id="add" onClick="add()">PlayGame</button>
<br>
<p id="tips"></p>
<p id="leiNum"></p>
<table border="2" id