.pic-outer-wrap {
    width: 800px;
    height: 270px;
    position: relative;
    overflow: hidden;
    margin: 20px auto;
}

.pic-outer-wrap:hover .btn-wrap {
    opacity: 1;
}

.pic-outer-wrap .pic-inner-wrap {
    width: 0;
    height: 270px;
    position: absolute;
    transition: position 0.5s;
    overflow: hidden;	
}

.pic-outer-wrap .pic-inner-wrap ul {
    float: left;
}

.pic-outer-wrap .pic-inner-wrap .pic-item {
    width: 400px;
    height: 270px;
    float: left;
    list-style: none;
    text-align: center;
    box-sizing: border-box;
    padding: 2px;
}

.pic-outer-wrap .pic-inner-wrap .pic-item div {
    width: 100%;
    height: 100%;
    box-sizing: border-box;
    overflow: hidden;
}

.pic-outer-wrap .pic-inner-wrap .pic-item img {
    width: 100% !important;
    height: 100% !important;
    object-fit: cover;
}

.pic-outer-wrap .btn-wrap {
    width: 100%;
    height: 50px;
    position: absolute;
    margin-top: -20px;
    top: 50%;
    opacity: 0;
    transition: opacity 0.4s;
}


.pic-outer-wrap .btn-wrap .btn-l,
.pic-outer-wrap .btn-wrap .btn-r {
    width: 30px;
    height: 100%;
    cursor: pointer;
    background-color: rgba(75, 75, 75, 0.5);
    margin: 0 10px;
    text-align: center;
    line-height: 28px;
    color: #ffffff;
    padding: 10px 0;
}

.btn-l {
    float: left;
}

.btn-r {
    float: right;
}