.banner {
    width: 100%;
    height: 200px;
    background: url("../images/partybg.jpg") no-repeat center center;
    background-size: cover;
    overflow: hidden;
}
/* 导航 */ 

.main .warp .nav .nav-box {
    display: inline-block;
    /* width: 49.3%; */
    height: 70px;
    box-sizing: border-box;
    font-size: 16px;
    cursor: pointer;
} 
 

.main .warp  .nav .nav-bg {
    background-color: #ff3f3f;
    /* width: 49.3%; */
    height: 70px;
    position: absolute;
    top: 0px;
    left: 0px;
}