/* ===== CSS Variables ===== */
:root {
    --color-primary: #1a1a2e;
    --color-secondary: #16213e;
    --color-accent: #00d9ff;
    --color-accent-hover: #00b8d9;
    --color-bg: #0f0f1a;
    --color-bg-card: #1a1a2e;
    --color-text: #e0e0e0;
    --color-text-muted: #8888a0;
    --color-border: #2a2a4a;
    
    --font-main: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-code: 'Fira Code', 'Consolas', monospace;
    
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 20px rgba(0, 217, 255, 0.3);
    
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-main);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
}

button {
    border: none;
    background: none;
    cursor: pointer;
    font-family: inherit;
}

/* ===== Animations ===== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

@keyframes gradientMove {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

/* ===== Header ===== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(15, 15, 26, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-border);
}

.header-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 24px;
    height: 70px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    font-size: 32px;
    animation: float 3s ease-in-out infinite;
}

.logo-text {
    font-size: 24px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--color-accent), #7b68ee);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-menu {
    display: flex;
    gap: 8px;
}

.nav-item {
    position: relative;
    padding: 8px 16px;
    font-size: 15px;
    font-weight: 500;
    color: var(--color-text-muted);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.nav-item::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--color-accent);
    transition: all var(--transition-normal);
    transform: translateX(-50%);
}

.nav-item:hover,
.nav-item.active {
    color: var(--color-accent);
}

.nav-item:hover::after,
.nav-item.active::after {
    width: 60%;
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 8px;
}

.mobile-menu-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    transition: all var(--transition-fast);
}

/* ===== Reading Progress ===== */
.reading-progress {
    position: fixed;
    top: 70px;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--color-border);
    z-index: 999;
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.reading-progress.visible {
    opacity: 1;
}

.reading-progress-bar {
    height: 100%;
    width: 0;
    background: linear-gradient(90deg, var(--color-accent), #7b68ee);
    transition: width 0.1s linear;
}

/* ===== Main Content ===== */
.main-content {
    min-height: calc(100vh - 70px);
    padding-top: 70px;
}

/* ===== Hero Section ===== */
.hero {
    position: relative;
    min-height: 500px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 80px 24px;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    inset: 0;
    background: 
        radial-gradient(ellipse at 20% 50%, rgba(0, 217, 255, 0.1) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 50%, rgba(123, 104, 238, 0.1) 0%, transparent 50%);
    z-index: 0;
}

.hero::after {
    content: '';
    position: absolute;
    inset: 0;
    background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%2300d9ff' fill-opacity='0.03'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
    z-index: 0;
}

.hero-content {
    position: relative;
    z-index: 1;
    animation: fadeInUp 0.8s ease-out;
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 700;
    margin-bottom: 16px;
    background: linear-gradient(135deg, #fff 0%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--color-text-muted);
    max-width: 600px;
    margin: 0 auto 32px;
}

.hero-tags {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

.hero-tag {
    padding: 8px 20px;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: 50px;
    font-size: 14px;
    color: var(--color-text-muted);
    transition: all var(--transition-fast);
}

.hero-tag:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
    box-shadow: var(--shadow-glow);
}

/* ===== Section Container ===== */
.section-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 60px 24px;
}

.section-header {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 40px;
}

.section-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--color-text);
}

.section-line {
    flex: 1;
    height: 1px;
    background: linear-gradient(90deg, var(--color-border), transparent);
}

/* ===== Article Grid ===== */
.article-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
}

/* ===== Article Card ===== */
.article-card {
    position: relative;
    height: 280px;
    perspective: 1000px;
    cursor: pointer;
    animation: fadeInUp 0.6s ease-out backwards;
}

.article-card:nth-child(1) { animation-delay: 0.1s; }
.article-card:nth-child(2) { animation-delay: 0.15s; }
.article-card:nth-child(3) { animation-delay: 0.2s; }
.article-card:nth-child(4) { animation-delay: 0.25s; }
.article-card:nth-child(5) { animation-delay: 0.3s; }
.article-card:nth-child(6) { animation-delay: 0.35s; }

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    transform-style: preserve-3d;
}

.article-card:hover .card-inner {
    transform: rotateY(180deg);
}

.card-front,
.card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.card-front {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    padding: 24px;
    display: flex;
    flex-direction: column;
    transition: all var(--transition-normal);
}

.article-card:hover .card-front {
    border-color: var(--color-accent);
    box-shadow: var(--shadow-glow);
}

.card-category {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 4px 12px;
    background: rgba(0, 217, 255, 0.1);
    border-radius: 50px;
    font-size: 12px;
    color: var(--color-accent);
    margin-bottom: 16px;
    width: fit-content;
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 12px;
    line-height: 1.4;
    flex: 1;
}

.card-meta {
    display: flex;
    align-items: center;
    gap: 16px;
    font-size: 13px;
    color: var(--color-text-muted);
}

.card-meta-item {
    display: flex;
    align-items: center;
    gap: 4px;
}

.card-back {
    background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
    border: 1px solid var(--color-accent);
    padding: 24px;
    transform: rotateY(180deg);
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.card-back-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-accent);
    margin-bottom: 16px;
}

.card-back-text {
    font-size: 14px;
    color: var(--color-text);
    line-height: 1.7;
    margin-bottom: 20px;
}

.card-back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    background: var(--color-accent);
    color: var(--color-bg);
    border-radius: var(--radius-md);
    font-weight: 500;
    font-size: 14px;
    transition: all var(--transition-fast);
}

.card-back-btn:hover {
    background: var(--color-accent-hover);
    transform: translateX(4px);
}

/* ===== About Page ===== */
.about-page {
    padding: 120px 24px 80px;
    max-width: 900px;
    margin: 0 auto;
    animation: fadeIn 0.6s ease-out;
}

.about-hero {
    text-align: center;
    margin-bottom: 60px;
}

.about-icon {
    font-size: 80px;
    margin-bottom: 24px;
    display: block;
    animation: float 3s ease-in-out infinite;
}

.about-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 16px;
    background: linear-gradient(135deg, var(--color-accent), #7b68ee);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.about-subtitle {
    font-size: 1.25rem;
    color: var(--color-text-muted);
}

.about-section {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: 32px;
    margin-bottom: 24px;
    animation: fadeInUp 0.6s ease-out backwards;
}

.about-section:nth-child(2) { animation-delay: 0.1s; }
.about-section:nth-child(3) { animation-delay: 0.2s; }

.about-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-accent);
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.about-section p {
    color: var(--color-text);
    line-height: 1.8;
}

.about-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px;
    margin-top: 16px;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px;
    background: rgba(0, 217, 255, 0.05);
    border-radius: var(--radius-md);
}

.feature-icon {
    font-size: 24px;
}

.feature-text {
    font-size: 14px;
    color: var(--color-text);
}

/* ===== Article Detail Page ===== */
.article-detail {
    max-width: 900px;
    margin: 0 auto;
    padding: 100px 24px 80px;
    animation: fadeIn 0.6s ease-out;
}

.article-detail-header {
    margin-bottom: 40px;
    text-align: center;
}

.article-detail-category {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 16px;
    background: rgba(0, 217, 255, 0.1);
    border-radius: 50px;
    font-size: 14px;
    color: var(--color-accent);
    margin-bottom: 20px;
}

.article-detail-title {
    font-size: clamp(1.75rem, 4vw, 2.5rem);
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: 20px;
    line-height: 1.3;
}

.article-detail-meta {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 24px;
    color: var(--color-text-muted);
    font-size: 14px;
}

.article-detail-content {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: 40px;
    line-height: 1.8;
}

.article-detail-content h2 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-accent);
    margin: 32px 0 16px;
}

.article-detail-content h2:first-child {
    margin-top: 0;
}

.article-detail-content p {
    margin-bottom: 16px;
    color: var(--color-text);
}

.article-detail-content ul,
.article-detail-content ol {
    margin-bottom: 16px;
    padding-left: 24px;
}

.article-detail-content li {
    margin-bottom: 8px;
    color: var(--color-text);
}

.article-detail-content code {
    font-family: var(--font-code);
    background: rgba(0, 217, 255, 0.1);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.9em;
    color: var(--color-accent);
}

.article-detail-content pre {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: 20px;
    margin-bottom: 20px;
    overflow-x: auto;
}

.article-detail-content pre code {
    background: none;
    padding: 0;
    font-size: 14px;
    line-height: 1.6;
}

.article-back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text);
    font-size: 14px;
    margin-top: 32px;
    transition: all var(--transition-fast);
}

.article-back-btn:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
}

/* ===== Footer ===== */
.footer {
    background: var(--color-primary);
    border-top: 1px solid var(--color-border);
    padding: 40px 24px;
}

.footer-container {
    max-width: 1400px;
    margin: 0 auto;
    text-align: center;
}

.footer-info p {
    color: var(--color-text-muted);
    font-size: 14px;
    margin-bottom: 8px;
}

.footer-info p:first-child {
    color: var(--color-text);
    font-weight: 500;
}

.footer-beian {
    margin-top: 16px;
}

.footer-beian a {
    color: var(--color-text-muted);
    transition: color var(--transition-fast);
}

.footer-beian a:hover {
    color: var(--color-accent);
}

/* ===== Back to Top ===== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 48px;
    height: 48px;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--color-accent);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all var(--transition-normal);
    z-index: 100;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    background: var(--color-accent);
    color: var(--color-bg);
    box-shadow: var(--shadow-glow);
}

/* ===== Empty State ===== */
.empty-state {
    text-align: center;
    padding: 80px 24px;
}

.empty-state-icon {
    font-size: 64px;
    margin-bottom: 24px;
    opacity: 0.5;
}

.empty-state-text {
    font-size: 1.25rem;
    color: var(--color-text-muted);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--color-bg);
        border-bottom: 1px solid var(--color-border);
        flex-direction: column;
        padding: 16px;
        gap: 4px;
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-normal);
    }

    .nav-menu.open {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }

    .mobile-menu-btn {
        display: flex;
    }

    .hero {
        min-height: 400px;
        padding: 60px 24px;
    }

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

    .article-card {
        height: 260px;
    }

    .section-container {
        padding: 40px 16px;
    }

    .article-detail-content {
        padding: 24px 16px;
    }

    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 40px;
        height: 40px;
    }
}