知识库：CSS3 实现的图片悬停的切换按钮

  <ul class="slides">      <input type="radio" name="radio-btn" id="img-1" checked />      <li class="slide-container">  		<div class="slide">  			<img src="http://farm9.staticflickr.com/8072/8346734966_f9cd7d0941_z.jpg" />          </div>  		<div class="nav">  			<label for="img-6" class="prev">&#x2039;</label>  			<label for="img-2" class="next">&#x203a;</label>  		</div>      </li>        <input type="radio" name="radio-btn" id="img-2" />      <li class="slide-container">          <div class="slide">            <img src="http://farm9.staticflickr.com/8504/8365873811_d32571df3d_z.jpg" />          </div>  		<div class="nav">  			<label for="img-1" class="prev">&#x2039;</label>  			<label for="img-3" class="next">&#x203a;</label>  		</div>      </li>        <input type="radio" name="radio-btn" id="img-3" />      <li class="slide-container">          <div class="slide">            <img src="http://farm9.staticflickr.com/8068/8250438572_d1a5917072_z.jpg" />          </div>  		<div class="nav">  			<label for="img-2" class="prev">&#x2039;</label>  			<label for="img-4" class="next">&#x203a;</label>  		</div>      </li>        <input type="radio" name="radio-btn" id="img-4" />      <li class="slide-container">          <div class="slide">            <img src="http://farm9.staticflickr.com/8061/8237246833_54d8fa37f0_z.jpg" />          </div>  		<div class="nav">  			<label for="img-3" class="prev">&#x2039;</label>  			<label for="img-5" class="next">&#x203a;</label>  		</div>      </li>        <input type="radio" name="radio-btn" id="img-5" />      <li class="slide-container">          <div class="slide">            <img src="http://farm9.staticflickr.com/8055/8098750623_66292a35c0_z.jpg" />          </div>  		<div class="nav">  			<label for="img-4" class="prev">&#x2039;</label>  			<label for="img-6" class="next">&#x203a;</label>  		</div>      </li>        <input type="radio" name="radio-btn" id="img-6" />      <li class="slide-container">          <div class="slide">            <img src="http://farm9.staticflickr.com/8195/8098750703_797e102da2_z.jpg" />          </div>  		<div class="nav">  			<label for="img-5" class="prev">&#x2039;</label>  			<label for="img-1" class="next">&#x203a;</label>  		</div>      </li>        <li class="nav-dots">        <label for="img-1" class="nav-dot" id="img-dot-1"></label>        <label for="img-2" class="nav-dot" id="img-dot-2"></label>        <label for="img-3" class="nav-dot" id="img-dot-3"></label>        <label for="img-4" class="nav-dot" id="img-dot-4"></label>        <label for="img-5" class="nav-dot" id="img-dot-5"></label>        <label for="img-6" class="nav-dot" id="img-dot-6"></label>      </li>  </ul>

  @import url(https://fonts.googleapis.com/css?family=Varela+Round);    html, body { background: #333 url("https://codepen.io/images/classy_fabric.png"); }    .slides {      padding: 0;      width: 609px;      height: 420px;      display: block;      margin: 0 auto;      position: relative;  }    .slides * {      user-select: none;      -ms-user-select: none;      -moz-user-select: none;      -khtml-user-select: none;      -webkit-user-select: none;      -webkit-touch-callout: none;  }    .slides input { display: none; }    .slide-container { display: block; }    .slide {      top: 0;      opacity: 0;      width: 609px;      height: 420px;      display: block;      position: absolute;        transform: scale(0);        transition: all .7s ease-in-out;  }    .slide img {      width: 100%;      height: 100%;  }    .nav label {      width: 200px;      height: 100%;      display: none;      position: absolute;    	  opacity: 0;      z-index: 9;      cursor: pointer;        transition: opacity .2s;        color: #FFF;      font-size: 156pt;      text-align: center;      line-height: 380px;      font-family: "Varela Round", sans-serif;      background-color: rgba(255, 255, 255, .3);      text-shadow: 0px 0px 15px rgb(119, 119, 119);  }    .slide:hover + .nav label { opacity: 0.5; }    .nav label:hover { opacity: 1; }    .nav .next { right: 0; }    input:checked + .slide-container  .slide {      opacity: 1;        transform: scale(1);        transition: opacity 1s ease-in-out;  }    input:checked + .slide-container .nav label { display: block; }    .nav-dots {  	width: 100%;  	bottom: 9px;  	height: 11px;  	display: block;  	position: absolute;  	text-align: center;  }    .nav-dots .nav-dot {  	top: -5px;  	width: 11px;  	height: 11px;  	margin: 0 4px;  	position: relative;  	border-radius: 100%;  	display: inline-block;  	background-color: rgba(0, 0, 0, 0.6);  }    .nav-dots .nav-dot:hover {  	cursor: pointer;  	background-color: rgba(0, 0, 0, 0.8);  }    input#img-1:checked ~ .nav-dots label#img-dot-1,  input#img-2:checked ~ .nav-dots label#img-dot-2,  input#img-3:checked ~ .nav-dots label#img-dot-3,  input#img-4:checked ~ .nav-dots label#img-dot-4,  input#img-5:checked ~ .nav-dots label#img-dot-5,  input#img-6:checked ~ .nav-dots label#img-dot-6 {  	background: rgba(0, 0, 0, 0.8);  }