如何在几个div上做透明背景来看父母的背景

Question

我有以下CSS代码：

#wrapper{
    height:500px;
    background: url('http://i.imgur.com/f1uCUEJ.jpg');
}
#menu:before{
    width:500px;
    height:60px;
    background: rgba(255,255,255,0.6);
    content: "";
    position: fixed;
    top:0;
    left: 0;
    border-radius: 0 0 10px 0;
}
#menu{
    position: fixed;
    top:60px;
    left: 0;
    background: rgba(255,255,255,0.6);
    height: 300px;
    width: 60px;
    border-radius: 0 0 10px 0;
}
#circle{
    position: fixed;
    width:150px;
    height:150px;
    border-radius: 150px;
    background: #000;
    top: 10px;
    left: 10px;
}
#circle2{
    position: fixed;
    width:120px;
    height:120px;
    border-radius: 120px;
    background: #fff;
    top: 25px;
    left: 25px;
}
#circle3{
    position: fixed;
    width:90px;
    height:90px;
    border-radius: 90px;
    background: #000;
    top: 40px;
    left: 40px;
}

#circle4{
    position: fixed;
    top: 54px;
    left: 54px;
}
.btn{
    border: none;
    display: block;
    margin: 1px;
    background: #fff;
    width:60px;
    height: 30px;    
    font-weight: 700;
    font-size: 17px;
}
#plus{
    border-radius: 30px 30px 0 0;
}
#minus{
    border-radius: 0 0 30px 30px;
}

并遵循HTML代码：

<div id="wrapper">
    <div id="menu"></div>
    <div id="circle">
        <div id="circle2">
            <div id="circle3">
                <div id="circle4">
                    <button id="plus" class="btn">+</button>
                    <button id="minus" class="btn">-</button>                    
                </div>
            </div>
        </div>
    </div>
</div>

你能帮助我理解我如何能够实现解决方案，这会产生“透明”的黑色圆圈而我只能看到图像吗？如果我现在将这种黑色作为 - background: rgba(0,0,0,0)。我可以看到“菜单”栏，我不想看到它们。

以下示例链接：http://jsfiddle.net/88Uxw/122/

Answer 1

这是你在找什么？的 FIDDLE

基本上不使用带有背景的圆圈，而是使用带边框的黑色并设置＆＃34;白色＆＃34;那些没有任何背景的人：

#circle{
    position: fixed;
    width:150px;
    height:150px;
    border-radius: 150px;
      border: 15px solid #000;
  box-sizing: border-box;
    top: 10px;
    left: 10px;
}

#circle2{
    position: fixed;
    width:120px;
    height:120px;
    border-radius: 120px;
    top: 25px;
    left: 25px;
}

#circle3{
    position: fixed;
    width:90px;
    height:90px;
    border-radius: 90px;
      border: 15px solid #000;
  box-sizing: border-box;
    top: 40px;
    left: 40px;
}

#circle4{
    position: fixed;
    top: 54px;
    left: 54px;
}

.btn{
    border: none;
    display: block;
    margin: 1px;
    background: transparent;
    width:60px;
    height: 30px;    
    font-weight: 700;
    font-size: 17px;
    border-bottom:1px solid #000;
}

请勿忘记添加box-sizing: border-box;以保持边框内的固定尺寸容器。

Answer 2

感谢@AlvaroMenéndez，我能够做我想做的事。这是我的问题的解决方案：

HTML：

<div id="wrapper">
    <div id="wrap">
        <div id="shape"></div>
    </div>
    <div id="wrap2">
        <div id="shape2"></div>
    </div>
    <div id="shape3">
        <button id="plus" class="btn">+</button>
        <button id="minus" class="btn">-</button>                    
    </div>
    <div id="left-menu"></div>
    <div id="top-menu"></div>
</div>

CSS：

#shape {
    width:200px;
    height:200px;
    position:fixed;
    overflow:hidden;
    top: 0;
    left: 0;
}

#shape:before {
    content:" ";
    position:absolute;
    width:100%;
    height:100%;
    left:15%; top:15%;
    border-radius:50%;
    box-shadow:0 0px 0 250px rgba(255,255,255,0.6);
}

#left-menu{
    background: rgba(255,255,255,0.6);
    width: 59px;
    height: 200px;
    position: fixed;
    top:200px;
    left: 0;
}

#top-menu{
    position: fixed;
    top: 0;
    left: 200px;
    background: rgba(255,255,255,0.6);
    width: 300px;
    height: 59px;
}

#shape2 {
  width: 140px;
  height: 140px;
  position: fixed;
  top: 60px;
  left: 60px;
}

#shape2:before {
  content: " ";
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  box-shadow: 0 0px 0 20px rgba(255,255,255,0.6);
}

#shape3{
    position: fixed;
    top: 69px;
    left: 69px;
}

.btn{
    border: none;
    display: block;
    margin: 1px;
    background: rgba(255,255,255,0.6);
    width:120px;
    height: 60px;    
    font-weight: 700;
    font-size: 17px;
}

.btn:hover{
    background: #fff;
}

#plus{
    border-radius: 100px 100px 0 0;
}

#minus{
    border-radius: 0 0 100px 100px;
}

工作示例：https://jsfiddle.net/L9aeu4o3/