:root {
    --brand-blue: #0364be;
    --main-blue:#0364be;
    --mobile-menu-bg: #f4f8fe;
    --text-dark: #222;
    --line: #eaeaea;
    --ease-smooth: cubic-bezier(0.16, 1, 0.3, 1);
}
::selection {
    color: #fff;
    background-color: var(--main-blue);
}

::-moz-selection {
    color: #fff;
    background-color: var(--main-blue);
}

::-webkit-selection {
    color: #fff;
    background-color: var(--main-blue);
}

::-webkit-scrollbar {
    width: 3px;
    height: 3px;
    background-color: #F5F5F5
}

::-webkit-scrollbar-track {
    border-radius: 10px;
    background-color: #E2E2E2
}

::-webkit-scrollbar-thumb {
    border-radius: 10px;
    background-color: var(--main-blue);
}

/* 置顶按钮 */
.back-to-top {
    position: fixed;
    right: 30px;
    bottom: 80px;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: #0364be;
    color: #fff;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 14px rgba(0, 0, 0, 0.18);
    opacity: 0;
    visibility: hidden;
    transform: translateY(16px);
    transition: opacity 0.3s ease, visibility 0.3s ease, transform 0.3s ease, background 0.2s ease;
    z-index: 9998;
}
.back-to-top.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}
.back-to-top:hover {
    background: #0282be;
}
.back-to-top svg {
    display: block;
}
@media (max-width: 768px) {
    .back-to-top {
        right: 18px;
        bottom: 60px;
        width: 42px;
        height: 42px;
    }
}

/* 顶部导航栏 */
.about_section_box .nav-tabs {
    display: flex;
    justify-content: center;
    list-style: none;
    border-bottom: 1px solid #dbdbdb;
    padding: 20px 0;
    margin-bottom: 50px;
}

.about_section_box .nav-tabs li {
    margin: 0 50px;
    font-size: 20px;
    color: #333;
    cursor: pointer;
    position: relative;
    padding-bottom: 10px;
}

.about_section_box .nav-tabs li.active {
    color: #333;
    font-weight: bold;
}

.about_section_box .nav-tabs li.active::after {
    content: '';
    position: absolute;
    bottom: -20px;
    left: 50%;
    transform: translateX(-50%);
    width: 40px;
    height: 2px;
    background-color: #00a0e9;
}