.banner_ad {
    display: flex;
    gap: 5px;
    flex-wrap: wrap;
    justify-content: space-between;
}

.banner_ad a {
    width: calc(50% - 5px);
    margin-bottom: 1rem;
    position: relative;
    overflow: hidden;
    border-radius: 6px;
}

.banner_ad a::before {
    content: "";
    display: block;
    padding-top: 25%; /* 4:1 宽高比 */
}

.banner_ad a img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
}

/* 响应式布局 */
@media screen and (max-width: 992px) {
    .banner_ad {
        gap: 0;
    }
    
    .banner_ad a {
        width: 100%;
    }
}