body {
    font-family: 'Quicksand', Arial, Helvetica, sans-serif;
    margin-top: 0;
    margin-bottom: 0;
    /* height: 100%; */
    background-color: #343434;
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
}

.overlay {
    position: fixed;
    background-color: rgba(0, 0, 0, 0.4);
    width: 100%;
    height: 100%;
    left: 0;
    z-index: 0;
    /* pointer-events: none; */
}

nav {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.5rem;
    text-align: center;
    /* position: relative; */
    /* position: sticky; */
    top:0;
    background-color: rgba(0, 0, 0, 0.4);
}

.horizontal-line {
    /* position: sticky; */
    top: 93px;
    border-top: 1px solid #ababab;
    z-index: 3;
}

.logo {
    font-size: 1.5rem;
    color: #c6c6c6;
}

.spacer {
    flex-grow: 1;
}

nav a {
    color: #c6c6c6;
    text-decoration: none;
    font-size: 1.2rem;
    border-radius: 20px;
    padding: 10px 15px;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

nav a:hover {
    background-color: #b3b3b3a0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

nav a.active {
    text-decoration: underline;
    text-decoration-color: #b3b3b3;
    text-decoration-thickness: 2.5px;
    text-underline-offset: 4px;
}

@media (max-width: 768px) {
    nav {
        flex-wrap: wrap;
    }

    .spacer {
        flex-grow: 0;
    }

    .logo {
        flex-basis: 100%;
        text-align: center;
    }
}

/* toggle switch */
.switch {
    opacity: 0.7;
    position: relative;
    display: inline-block;
    width: 70px;
    height: 34px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

/* slider */
/* slider background */
.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #ccc;
    transition: .4s;
    border-radius: 34px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 26px;
    width: 26px;
    left: 4px;
    bottom: 4px;
    background-color: white;
    transition: .4s;
    border-radius: 50%;
}

/* switch-on bgc */
input:checked + .slider {
    background-color: #a3f9ff;
}

input:checked + .slider:before {
    transform: translateX(35px); /* 调整为按钮滑动到右侧 */
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

/* text format */
.switch-text {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    font-size: 1rem;
    font-weight: 600;
    color: #666;
}

.switch-text:first-of-type {
    z-index: 1;
    left: 8.5px; /* 左侧的 "中" 文字 */
}

.switch-text:last-of-type {
    right: 7px; /* 右侧的 "EN" 文字 */
}
/* end */

/* Amimation */
nav a, .horizontal-line {
    transition: opacity 0.5s ease;
}

nav a.fade-out, .horizontal-line.fade-out {
    opacity: 0;
}

nav a.fade-i, .horizontal-line.fade-out {
    opacity: 1;
}
/* end */

footer {
    position: relative;
    bottom: 0;
    left: 0;
    width: 100%;
    text-align: center;
    font-size: 0.9rem;
    color: #666;
}

.watermarking {
    display: inline-block;
    text-align: center;
}

.beian {
    display: inline-block;
}

.beian a {
    color: #666;
    text-decoration: none;
}

.beian a:hover {
    text-decoration: underline;
    color: #666;
}

@keyframes fadeInUp {
    0% {
        opacity: 0;
        transform: translateY(40px);
    }
    100% {
        opacity: 1;
        transform: translateY(0);
    }
}