#container {
    width:1000px;
    height: 350px;
    overflow: hidden;/*隐藏超出的图片*/
    position: relative;
}
#list {
    width:7000px;
    height: 350px;
    position: absolute;
    z-index: 1;
}
#list img {
    float: left;
}
#buttons {
    position: absolute;
    height: 10px;
    width: 100px;
    z-index: 2;
    bottom: 20px;
    left: 50%;
}
#buttons span {
    cursor: pointer;/*cursor属性定义了鼠标指针放在一个元素边界范围内时所用的光标形状*/
    float: left;
    border: 1px solid #fff;
    width: 10px;
    height: 10px;
    order-radius: 50%;
    background: #333;
    margin-right: 5px;
}

#buttons .on {
    background: orangered;
}
.arrow {
    cursor: pointer;
    display: none;
    line-height: 39px;
    text-align: center;
    font-size: 36px;
    font-weight: bold;
    width: 40px;
    height: 40px;
    position: absolute;
    z-index: 2;
    top: 180px;
    background-color: RGBA(0,0,0,.3);
    color: #fff;
}
.arrow:hover {
    background-color: RGBA(0,0,0,.7);
}
#container:hover .arrow {
    display: block;
}
#prev {
    left: 20px;
}
#next {
    right: 20px;
}