* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    line-height: 1.6;
    color: #1a2a3a;
    background-color: #ffffff;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

a {
    text-decoration: none;
    transition: color 0.3s;
    color: inherit;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

ul,
li {
    list-style: none;
}

.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 24px;
}


.site-header {
    position: sticky;
    top: 0;
    background: #ffffff;
    border-bottom: 1px solid #eaeef2;
    box-shadow: 0 4px 12px rgba(0, 20, 30, 0.03);
    z-index: 1000;
    transition: background 0.3s, box-shadow 0.3s, border-color 0.3s;
}

.site-header.scrolled {
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(8px);
    box-shadow: 0 8px 20px rgba(0, 20, 30, 0.1);
    border-bottom-color: #c0d4e8;
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.logo a {
    font-size: 1.8rem;
    font-weight: 600;
    text-decoration: none;
    color: #0b2b40;
    letter-spacing: -0.5px;
}

.logo span {
    font-weight: 300;
    color: #5e8ca5;
}

.hamburger {
    display: none;
    background: none;
    border: none;
    font-size: 2rem;
    cursor: pointer;
    color: #1e3b4f;
    padding: 0 10px;
}

.main-nav ul {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.main-nav a {
    text-decoration: none;
    font-weight: 500;
    color: #2c4b63;
    font-size: 1.05rem;
    transition: color 0.2s;
    padding-bottom: 4px;
    border-bottom: 2px solid transparent;
}

.main-nav a:hover,
.main-nav a.active {
    color: #0b2b40;
    border-bottom-color: #5e8ca5;
}

/* ---------- top notice ---------- */
.top-notice {
    background: #f0f7fc;
    border-bottom: 1px solid #d4e2ed;
    padding: 14px 0;
    font-size: 1rem;
}

.top-notice p {
    display: flex;
    align-items: center;
    gap: 8px;
}

.top-notice a {
    color: #005f8c;
    font-weight: 500;
    text-decoration: none;
    border-bottom: 1px dotted;
}

.top-notice a:hover {
    color: #002d44;
}

/* ---------- section headers ---------- */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: 40px 0 24px;
}

.section-header h2 {
    font-size: 2rem;
    font-weight: 500;
    color: #0b2b40;
    letter-spacing: -0.02em;
}

.view-all {
    text-decoration: none;
    color: #3c6e8f;
    font-weight: 500;
    border-bottom: 1px solid;
    padding-bottom: 2px;
}

.view-all:hover {
    color: #0b2b40;
}

/* ---------- cards base ---------- */
.card {
    background: white;
    border-radius: 20px;
    overflow: hidden;
    box-shadow: 0 6px 18px rgba(0, 30, 40, 0.04);
    transition: transform 0.25s ease, box-shadow 0.3s;
    border: 1px solid #edf2f7;
}

.card:hover {
    transform: translateY(-6px);
    box-shadow: 0 16px 28px rgba(20, 50, 70, 0.1);
}

.card-img {
    aspect-ratio: 4/3;
    overflow: hidden;
    background: #e4edf2;
}

.card-img img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: scale 0.3s;
}

.card:hover .card-img img {
    scale: 1.02;
}

.tag {
    display: inline-block;
    background: #e1ecf5;
    color: #1f506b;
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.5px;
    padding: 4px 10px;
    border-radius: 40px;
    margin: 16px 0 8px 16px;
}

.card h3,
.card h4 {
    margin: 0 16px 8px;
    line-height: 1.4;
}

.card h3 a,
.card h4 a {
    text-decoration: none;
    color: #0a2535;
}

.card h3 a:hover {
    color: #3a6d8c;
}

.card h3 {
    font-size: 1.6rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.card .excerpt {
    margin: 0 16px 16px;
    color: #3b5568;
    font-size: 1.1rem;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.meta {
    margin: 0 16px 18px;
    font-size: 0.85rem;
    color: #6a7f91;
    border-top: 1px dashed #d9e2ec;
    padding-top: 12px;
}

/* ---------- horizontal cards (used in index) ---------- */
.horizontal-cards {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.card-horizontal {
    display: flex;
    flex-direction: row;
    align-items: center;
}

.card-horizontal .card-img {
    width: 30%;
    min-width: 200px;
}

.card-horizontal .card-content {
    flex: 1;
}

/* ---------- mixed tech section (index) ---------- */
.cards-mixed {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.card-vertical {
    flex: 1 1 220px;
    min-width: 240px;
}

.card-list {
    flex: 2 1 300px;
    background: #f8fafd;
    border-radius: 20px;
    padding: 20px;
}

.list-item {
    padding: 16px 0;
    border-bottom: 1px solid #dde6ef;
}

.list-item:last-child {
    border-bottom: none;
}

.list-item h4 {
    margin: 6px 0 4px;
    font-size: 1.1rem;
}

.list-item .tag {
    margin: 0 0 6px 0;
}

/* ---------- featured section (index) ---------- */
.featured-section {
    margin: 60px 0;
}

.featured-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 32px;
}

.featured-card {
    background: #ffffff;
    border-radius: 28px;
    padding: 20px 20px 28px;
    box-shadow: 0 12px 28px rgba(0, 35, 50, 0.06);
    border: 1px solid #e3ebf3;
}

.featured-card .card-img {
    border-radius: 18px;
}

.featured-card h3 {
    font-size: 1.5rem;
    margin: 16px 16px 12px;
}

/* ---------- topics cloud (index) ---------- */
.topics-section {
    margin: 40px 0 80px;
}

.topics-cloud {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 20px;
}

.topic {
    background: #ecf3f9;
    color: #205882;
    padding: 8px 18px;
    border-radius: 60px;
    font-size: 0.95rem;
    font-weight: 500;
    transition: background 0.2s;
    cursor: default;
}

.topic:hover {
    background: #d4e2f0;
}

/* ---------- breadcrumb (category & article) ---------- */
.breadcrumb-nav {
    margin: 24px 0 16px;
}

.breadcrumb {
    display: flex;
    flex-wrap: wrap;
    list-style: none;
    padding: 12px 20px;
    background: #f5faff;
    border-radius: 60px;
    font-size: 0.95rem;
    border: 1px solid #d9e6f5;
}

.breadcrumb li {
    display: flex;
    align-items: center;
}

.breadcrumb li:not(:last-child)::after {
    content: "›";
    margin: 0 12px;
    color: #849fb2;
    font-size: 1.2rem;
    line-height: 1;
}

.breadcrumb a {
    text-decoration: none;
    color: #1f5575;
    font-weight: 500;
}

.breadcrumb a:hover {
    text-decoration: underline;
    color: #0b2b40;
}

.breadcrumb li[aria-current="page"] {
    color: #2f4d66;
    font-weight: 600;
}

/* ---------- category page layout ---------- */
.category-layout {
    display: flex;
    gap: 48px;
    margin: 40px auto;
}

.category-main {
    flex: 0 0 70%;
}

.category-sidebar {
    flex: 0 0 28%;
}

.category-title {
    font-size: 2.2rem;
    font-weight: 500;
    color: #052c3f;
    margin-bottom: 12px;
}

.result-count {
    font-size: 1.2rem;
    font-weight: 300;
    color: #6a7f91;
}

.filter-bar {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 20px 0 30px;
}

.custom-select select {
    padding: 10px 30px 10px 16px;
    border: 1px solid #bccfdf;
    border-radius: 40px;
    background: white;
    font-size: 0.95rem;
    color: #1a2a3a;
    appearance: none;
    background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%233f6b89' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'><polyline points='6 9 12 15 18 9'/></svg>");
    background-repeat: no-repeat;
    background-position: right 12px center;
    cursor: pointer;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 28px;
    margin-bottom: 48px;
}

/* ---------- pagination ---------- */
.pagination {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin: 30px 0 20px;
}

.pagination a,
.pagination span {
    display: inline-block;
    padding: 8px 14px;
    border-radius: 40px;
    background: #f2f8ff;
    color: #1e4d70;
    text-decoration: none;
    border: 1px solid #c9daea;
}

.pagination a.active {
    background: #1e4d70;
    color: white;
    border-color: #1e4d70;
}

.pagination a.disabled {
    opacity: 0.4;
    pointer-events: none;
}

.pagination a:hover:not(.disabled) {
    background: #d7e4f0;
}

/* ---------- sidebar widgets (category & article) ---------- */
.sidebar-widget {
    background: #f7fbfe;
    border-radius: 24px;
    padding: 24px;
    margin-bottom: 32px;
}

.sidebar-widget h3 {
    font-size: 1.3rem;
    margin-bottom: 16px;
}

.popular-list li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0;
    border-bottom: 1px solid #d8e5f0;
}

.popular-list a {
    text-decoration: none;
    color: #0b2b40;
    font-weight: 500;
}

.views {
    font-size: 0.8rem;
    color: #668097;
}

.tag-list {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.tag-list .tag {
    margin: 0;
    cursor: default;
}

/* author widget (sidebar) */
.author-widget {
    text-align: center;
}

.author-avatar {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    overflow: hidden;
    margin: 0 auto 16px;
    border: 3px solid white;
    box-shadow: 0 6px 14px rgba(0, 50, 70, 0.1);
}

.author-avatar img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.author-widget h3 {
    font-size: 1.4rem;
    margin-bottom: 4px;
    color: #0b2b40;
}

.author-role {
    color: #4f728b;
    font-size: 0.9rem;
    margin-bottom: 12px;
    font-weight: 500;
}

.author-bio {
    color: #2c4f69;
    margin-bottom: 16px;
    font-size: 0.95rem;
}

.author-link {
    display: inline-block;
    padding: 8px 20px;
    background: #e1effa;
    border-radius: 40px;
    text-decoration: none;
    color: #1a4f73;
    font-weight: 500;
    font-size: 0.9rem;
    transition: background 0.2s;
}

.author-link:hover {
    background: #cde2f5;
}

/* post list (sidebar) */
.post-list {
    list-style: none;
}

.post-list li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 0;
    border-bottom: 1px dashed #c7d9e8;
}

.post-list li:last-child {
    border-bottom: none;
}

.post-list a {
    text-decoration: none;
    color: #10405c;
    font-weight: 500;
    flex: 1;
    padding-right: 12px;
}

.post-list a:hover {
    color: #002d44;
    text-decoration: underline;
}

.post-date {
    font-size: 0.8rem;
    color: #6a8299;
    white-space: nowrap;
}

/* category list (sidebar) */
.category-list {
    list-style: none;
}

.category-list li {
    padding: 8px 0;
    border-bottom: 1px solid #d4e2ee;
}

.category-list a {
    display: flex;
    justify-content: space-between;
    text-decoration: none;
    color: #135072;
    font-weight: 500;
}

.category-list a:hover {
    color: #002a41;
}

.category-list .count {
    background: #e0ebf5;
    padding: 2px 10px;
    border-radius: 40px;
    font-size: 0.8rem;
    color: #1a4b6e;
}

/* ---------- article detail page ---------- */
.full-article-detail {
    max-width: 100%;
}

.article-header-detail h1 {
    font-size: 2.8rem;
    font-weight: 600;
    line-height: 1.2;
    color: #021c2c;
    margin: 0 0 0.5rem;
}

.article-subhead {
    font-size: 1.3rem;
    font-weight: 400;
    color: #3f5f78;
    margin-bottom: 1.5rem;
    border-left: 4px solid #9bb8d4;
    padding-left: 1rem;
}

.meta-line {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    margin: 1.5rem 0 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid #d5e3ef;
}

.meta-left {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
}

.author-mini-avatar {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    object-fit: cover;
}

.author-name {
    font-weight: 600;
    color: #1c4d70;
}

.sep {
    color: #96aebb;
}

.meta-left time,
.updated {
    color: #3c5e77;
    font-size: 0.95rem;
}

.meta-right .views {
    background: #ecf4fb;
    padding: 4px 12px;
    border-radius: 40px;
    font-size: 0.9rem;
    color: #1e506e;
}

.article-body {
    font-size: 0.985rem;
    letter-spacing: 0.2px;
    color: #171717;
    line-height: 1.75;
    margin: 2rem 0;
}

.article-body img {
    margin: 0 auto;
}

.article-body p {
    margin-bottom: 1.8rem;
}

.article-body h2 {
    font-size: 1.8rem;
    margin: 2.5rem 0 1rem;
    color: #052c3f;
    font-weight: 600;
}

.article-body h3 {
    font-size: 1.4rem;
    margin: 2rem 0 0.8rem;
    color: #15475f;
}

.author-detailed-block {
    display: flex;
    gap: 1.8rem;
    background: #f5faff;
    border-radius: 32px;
    padding: 2rem;
    margin: 2.5rem 0 1.5rem;
    border: 1px solid #cfe0f0;
}

.author-detailed-avatar img {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid white;
    box-shadow: 0 6px 12px rgba(0, 40, 60, 0.1);
}

.author-detailed-info {
    flex: 1;
}

.author-detailed-info h3 {
    font-size: 1.6rem;
    margin-bottom: 0.2rem;
    color: #0b2b40;
}

.author-detailed-role {
    color: #386481;
    font-weight: 500;
    margin-bottom: 0.8rem;
}

.author-detailed-bio {
    color: #1c3f55;
    margin-bottom: 1.2rem;
    line-height: 1.6;
}

.author-detailed-links a {
    display: inline-block;
    margin-right: 1.5rem;
    text-decoration: none;
    color: #1b6290;
    font-weight: 500;
    border-bottom: 1px dotted;
}

.author-detailed-links a:hover {
    color: #0b2b40;
}

.share-buttons-block {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
    margin: 2rem 0 2.5rem;
    padding: 1.5rem 0;
    border-top: 1px solid #dae6f2;
    border-bottom: 1px solid #dae6f2;
}

.share-label {
    font-weight: 600;
    color: #1a3c52;
    margin-right: 0.5rem;
}

.share-buttons-block button {
    background: #e5f0fa;
    border: none;
    padding: 8px 20px;
    border-radius: 40px;
    font-size: 0.9rem;
    cursor: pointer;
    border: 1px solid #b5d0e8;
    transition: background 0.2s;
}

.share-buttons-block button:hover {
    background: #cde2f5;
}

.comments-section {
    margin: 60px 0 40px;
    border-top: 2px solid #d5e4f0;
    padding-top: 40px;
}

.comment-list {
    margin: 30px 0;
}

.comment {
    display: flex;
    gap: 20px;
    margin-bottom: 32px;
}

.comment-avatar {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    overflow: hidden;
    flex-shrink: 0;
}

.comment-avatar img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.comment-body {
    background: #f2f8fe;
    padding: 16px 22px;
    border-radius: 24px;
    flex: 1;
}

.comment-date {
    font-size: 0.8rem;
    color: #557c9a;
    margin-left: 12px;
}

.comment-form {
    background: #f1f8ff;
    border-radius: 30px;
    padding: 32px;
}

.comment-form h3 {
    margin-bottom: 20px;
}

.comment-form input,
.comment-form textarea {
    width: 100%;
    padding: 14px 20px;
    border: 1px solid #bccfdf;
    border-radius: 40px;
    margin-bottom: 16px;
    font-size: 1rem;
}

.comment-form textarea {
    border-radius: 28px;
}

.comment-form button {
    background: #1e4d70;
    color: white;
    border: none;
    padding: 14px 36px;
    border-radius: 40px;
    font-size: 1rem;
    cursor: pointer;
}

.comment-form button:hover {
    background: #0b3855;
}

.related-articles {
    margin: 3.5rem 0 1rem;
}

.related-articles h2 {
    font-size: 1.8rem;
    margin-bottom: 1.5rem;
    color: #0b2b40;
}

.related-grid {
    display: flex;
    flex-direction: column;
    gap: 1.2rem;
}

.related-card {
    display: flex;
    gap: 1rem;
    background: #fafdff;
    border-radius: 18px;
    padding: 0.8rem;
    border: 1px solid #e0eefc;
    transition: background 0.2s;
}

.related-card:hover {
    background: #f0f7ff;
}

.related-img {
    flex-shrink: 0;
    width: 100px;
    height: 75px;
    border-radius: 12px;
    overflow: hidden;
}

.related-img img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.related-content {
    flex: 1;
}

.related-content .tag {
    margin: 0 0 4px 0;
    display: inline-block;
}

.related-content h4 {
    font-size: 1rem;
    margin: 4px 0 6px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.related-content h4 a {
    text-decoration: none;
    color: #0a2e42;
}

.related-content h4 a:hover {
    text-decoration: underline;
}

.related-content .meta {
    margin: 0;
    border: none;
    padding: 0;
    font-size: 0.8rem;
}

/* ---------- author page (full width) ---------- */

.author-header {
    display: flex;
    gap: 3rem;
    align-items: flex-start;
    margin: 3rem 0;
    background: #f5faff;
    border-radius: 48px;
    padding: 2.5rem;
    border: 1px solid #d9e6f5;
}

.author-header-avatar {
    flex-shrink: 0;
}

.author-header-avatar img {
    width: 180px;
    height: 180px;
    border-radius: 50%;
    object-fit: cover;
    border: 5px solid white;
    box-shadow: 0 12px 24px rgba(0, 40, 60, 0.15);
}

.author-header-info {
    flex: 1;
}

.author-header-info h1 {
    font-size: 3rem;
    font-weight: 600;
    color: #021c2c;
    margin: 0 0 0.25rem;
    line-height: 1.2;
}

.author-header-info .author-role {
    font-size: 1.4rem;
    font-weight: 400;
    color: #386481;
    margin-bottom: 1rem;
    border-left: 4px solid #9bb8d4;
    padding-left: 1rem;
}

.author-header-info .author-bio {
    font-size: 1.1rem;
    line-height: 1.6;
    color: #1d3e55;
    margin-bottom: 1.5rem;
}

.author-social-links a {
    display: inline-block;
    margin-right: 1.5rem;
    text-decoration: none;
    color: #1b6290;
    font-weight: 500;
    border-bottom: 1px dotted;
    padding-bottom: 2px;
}

.author-social-links a:hover {
    color: #0b2b40;
}

.author-stats {
    display: flex;
    gap: 2rem;
    margin: 2rem 0 2.5rem;
}

.stat-item {
    background: #ffffff;
    border-radius: 60px;
    padding: 0.8rem 2rem;
    box-shadow: 0 4px 12px rgba(0, 30, 50, 0.05);
    border: 1px solid #cde0f0;
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: 600;
    color: #003153;
    line-height: 1.2;
}

.stat-label {
    font-size: 0.9rem;
    color: #506e87;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.author-detailed-bio {
    margin: 2.5rem 0;
    font-size: 1.1rem;
    line-height: 1.7;
    color: #1d3649;
}

.author-works h2 {
    font-size: 2rem;
    margin: 3rem 0 1.5rem;
    color: #0b2b40;
    border-bottom: 2px solid #c5dbf0;
    padding-bottom: 0.5rem;
}

.author-articles-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
    margin-top: 2rem;
}

.author-article-card {
    background: white;
    border-radius: 24px;
    overflow: hidden;
    box-shadow: 0 6px 16px rgba(0, 35, 50, 0.04);
    border: 1px solid #e2edf8;
    transition: transform 0.2s, box-shadow 0.2s;
}

.author-article-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 16px 28px rgba(0, 45, 70, 0.1);
}

.author-article-card .card-img {
    aspect-ratio: 16/9;
    overflow: hidden;
}

.author-article-card .card-img img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: scale 0.3s;
}

.author-article-card:hover .card-img img {
    scale: 1.02;
}

.author-article-card .card-content {
    padding: 1.2rem 1.5rem 1.8rem;
}

.author-article-card .tag {
    margin: 0 0 0.5rem 0;
    display: inline-block;
}

.author-article-card h3 {
    font-size: 1.25rem;
    margin: 0 0 0.5rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.author-article-card h3 a {
    text-decoration: none;
    color: #0a2535;
}

.author-article-card h3 a:hover {
    color: #1e5f86;
}

.author-article-card .meta {
    margin: 0.8rem 0 0;
    border: none;
    padding: 0;
    font-size: 0.85rem;
    color: #617f98;
}

/* ---------- footer ---------- */
.site-footer {
    background: #f6faff;
    border-top: 1px solid #d6e2f0;
    margin-top: 30px;
    padding: 20px 0 20px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 32px;
}

.footer-col .logo {
    font-size: 1.6rem;
    margin-bottom: 16px;
}

.footer-col h4 {
    font-size: 1.1rem;
    color: #133f57;
    margin-bottom: 16px;
}

.footer-col ul {
    list-style: none;
}

.footer-col li {
    margin-bottom: 10px;
}

.footer-col a {
    text-decoration: none;
    color: #3b637b;
}

.footer-col a:hover {
    color: #0b2b40;
    text-decoration: underline;
}

.footer-bottom {
    text-align: center;
    font-size: 0.9rem;
    color: #55748b;
}

.footer-bottom p {
    text-align: center;
    margin: 0;
}

.footer-bottom a {
    font-size: 0.9rem;
    color: #55748b;
}

/* ---------- back to top ---------- */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: #ffffff;
    border: 1px solid #bcd2e6;
    border-radius: 50%;
    font-size: 1.8rem;
    color: #1e4d70;
    cursor: pointer;
    box-shadow: 0 6px 14px rgba(0, 45, 70, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity 0.2s, transform 0.2s;
    pointer-events: none;
    z-index: 99;
}

.back-to-top.show {
    opacity: 1;
    pointer-events: auto;
}

.back-to-top:hover {
    background: #e6f0fa;
    transform: translateY(-3px);
}

/* ---------- responsive ---------- */
@media (max-width: 920px) {
    .footer-grid {
        grid-template-columns: 1fr 1fr;
        gap: 30px;
    }

    .featured-grid {
        grid-template-columns: 1fr;
    }

    .category-layout {
        flex-direction: column;
    }

    .category-sidebar {
        margin-top: 48px;
    }
}

@media (max-width: 768px) {
    .cards-mixed {
        display: grid;
        grid-template-columns: repeat(1, 1fr);
        gap: 24px;
    }

    .meta-left {
        font-size: 0.75rem;
        gap: 0.3rem;
    }

    .meta-left time,
    .updated,
    .meta-right .views {
        font-size: 0.75rem;
    }

    .site-header {
        position: relative;
    }

    .header-container {
        height: 54px;
    }

    .hamburger {
        display: block;
    }

    .main-nav {
        position: absolute;
        top: 54px;
        left: 0;
        width: 100%;
        background: #ffffff;
        border-top: 1px solid #cddeec;
        box-shadow: 0 12px 20px rgba(0, 0, 0, 0.05);
        display: none;
        padding: 20px 0;
    }

    .main-nav.show {
        display: block;
    }

    .main-nav ul {
        flex-direction: column;
        align-items: center;
        gap: 1rem;
    }

    .horizontal-cards .card-horizontal {
        flex-direction: column;
        align-items: flex-start;
    }

    .card-horizontal .card-img {
        width: 100%;
    }

    .category-grid {
        grid-template-columns: 1fr;
    }

    .article-header-detail h1 {
        font-size: 1.4rem;
    }

    .article-subhead {
        font-size: 1.1rem;
    }

    .author-detailed-block {
        flex-direction: column;
        align-items: center;
        text-align: center;
    }

    .meta-line {
        gap: 0.5rem;
    }

    .author-header {
        flex-direction: column;
        align-items: center;
        text-align: center;
        padding: 1.8rem;
    }

    .author-header-info .author-role {
        border-left: none;
        padding-left: 0;
    }

    .author-stats {
        justify-content: center;
    }

    .author-articles-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .footer-grid {
        grid-template-columns: 1fr;
    }

    .topics-cloud {
        justify-content: center;
    }

    .breadcrumb {
        padding: 10px 16px;
        font-size: 0.85rem;
    }

    .breadcrumb li:not(:last-child)::after {
        margin: 0 6px;
    }

    .author-avatar {
        width: 80px;
        height: 80px;
    }

    .author-header h1 {
        font-size: 2.2rem;
    }

    .author-header-avatar img {
        width: 140px;
        height: 140px;
    }

    .stat-item {
        padding: 0.5rem 1rem;
    }

    .stat-number {
        font-size: 1.5rem;
    }
}