/* Calibre Download Site - Style Sheet */
:root {
    --primary: #1a237e;
    --primary-light: #283593;
    --primary-dark: #0d1452;
    --accent: #3f51b5;
    --accent-light: #5c6bc0;
    --text-primary: #1a1a2e;
    --text-secondary: #4a4a6a;
    --text-light: #6b6b8a;
    --bg-primary: #ffffff;
    --bg-secondary: #f5f6fa;
    --bg-tertiary: #eef0f7;
    --border-color: #e0e3ef;
    --success: #2e7d32;
    --shadow-sm: 0 1px 3px rgba(26, 35, 126, 0.08);
    --shadow-md: 0 4px 12px rgba(26, 35, 126, 0.12);
    --shadow-lg: 0 8px 32px rgba(26, 35, 126, 0.16);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --max-width: 1200px;
    --transition: all 0.3s ease;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
    color: var(--text-primary);
    background: var(--bg-primary);
    line-height: 1.7;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--primary); }

.container { max-width: var(--max-width); margin: 0 auto; padding: 0 24px; }

/* Header */
.site-header {
    background: var(--primary);
    color: #fff;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 24px;
    max-width: var(--max-width);
    margin: 0 auto;
    height: 64px;
}

.site-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    color: #fff;
    font-size: 1.25rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

.site-logo svg { flex-shrink: 0; }

.site-logo:hover { color: #e8eaf6; }

.main-nav { display: flex; align-items: center; gap: 0; }

.main-nav a {
    color: rgba(255,255,255,0.85);
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition);
}

.main-nav a:hover, .main-nav a.active {
    color: #fff;
    background: rgba(255,255,255,0.12);
}

.nav-toggle { display: none; background: none; border: none; color: #fff; cursor: pointer; padding: 8px; }

/* Hero */
.hero {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 50%, var(--accent) 100%);
    color: #fff;
    padding: 80px 0;
    text-align: center;
}

.hero h1 {
    font-size: 2.8rem;
    font-weight: 800;
    margin-bottom: 16px;
    letter-spacing: -0.03em;
    line-height: 1.2;
}

.hero .subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
    max-width: 640px;
    margin: 0 auto 32px;
    line-height: 1.8;
}

.hero .version-badge {
    display: inline-block;
    background: rgba(255,255,255,0.15);
    border: 1px solid rgba(255,255,255,0.3);
    padding: 6px 18px;
    border-radius: 20px;
    font-size: 0.85rem;
    margin-bottom: 24px;
    backdrop-filter: blur(4px);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 14px 32px;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    border: none;
    transition: var(--transition);
    text-decoration: none;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
    box-shadow: var(--shadow-md);
}

.btn-primary:hover {
    background: var(--primary-light);
    color: #fff;
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: #fff;
    color: var(--primary);
    border: 2px solid var(--primary);
}

.btn-secondary:hover {
    background: var(--bg-secondary);
    color: var(--primary);
    transform: translateY(-2px);
}

.btn-light {
    background: #fff;
    color: var(--primary);
    box-shadow: var(--shadow-sm);
}

.btn-light:hover {
    background: var(--bg-secondary);
    color: var(--primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-lg { padding: 16px 40px; font-size: 1.1rem; }

.btn-group { display: flex; gap: 16px; flex-wrap: wrap; justify-content: center; }

/* Sections */
.section { padding: 72px 0; }
.section-alt { background: var(--bg-secondary); }

.section-title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 12px;
    color: var(--primary);
    letter-spacing: -0.02em;
}

.section-desc {
    text-align: center;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 48px;
    font-size: 1.05rem;
}

/* Cards */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
}

.card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 32px;
    transition: var(--transition);
}

.card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-4px);
    border-color: var(--accent-light);
}

.card-icon {
    width: 48px;
    height: 48px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    color: var(--primary);
}

.card h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.7;
}

/* Download Page */
.download-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin-top: 40px;
}

.download-card {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 36px 28px;
    text-align: center;
    transition: var(--transition);
}

.download-card:hover {
    border-color: var(--accent);
    box-shadow: var(--shadow-lg);
}

.download-card .os-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 20px;
    color: var(--primary);
}

.download-card h3 {
    font-size: 1.3rem;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.download-card .meta {
    color: var(--text-light);
    font-size: 0.85rem;
    margin-bottom: 20px;
}

.download-card .btn { width: 100%; justify-content: center; }

/* FAQ */
.faq-list { max-width: 800px; margin: 0 auto; }

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: 12px;
    overflow: hidden;
    transition: var(--transition);
}

.faq-item:hover { border-color: var(--accent-light); }

.faq-question {
    width: 100%;
    background: none;
    border: none;
    padding: 20px 24px;
    text-align: left;
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
}

.faq-question::after {
    content: "+";
    font-size: 1.4rem;
    color: var(--accent);
    transition: var(--transition);
    flex-shrink: 0;
}

.faq-item.active .faq-question::after { content: "-"; }

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
}

.faq-answer-inner {
    padding: 0 24px 20px;
    color: var(--text-secondary);
    line-height: 1.8;
}

.faq-item.active .faq-answer { max-height: 500px; }

/* Footer */
.site-footer {
    background: var(--primary-dark);
    color: rgba(255,255,255,0.7);
    padding: 48px 0 24px;
}

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

.footer-brand p { margin-top: 12px; font-size: 0.9rem; line-height: 1.7; }

.footer-links h4 {
    color: #fff;
    font-size: 0.95rem;
    margin-bottom: 16px;
    font-weight: 600;
}

.footer-links a {
    display: block;
    color: rgba(255,255,255,0.6);
    padding: 4px 0;
    font-size: 0.9rem;
    transition: var(--transition);
}

.footer-links a:hover { color: #fff; }

.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.1);
    padding-top: 24px;
    text-align: center;
    font-size: 0.85rem;
}

/* Content Pages */
.page-header {
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    color: #fff;
    padding: 56px 0 48px;
    text-align: center;
}

.page-header h1 { font-size: 2.2rem; font-weight: 700; margin-bottom: 12px; }
.page-header p { opacity: 0.85; font-size: 1.05rem; max-width: 560px; margin: 0 auto; }

.content-section { padding: 56px 0; }
.content-block { max-width: 800px; margin: 0 auto; }
.content-block h2 { font-size: 1.5rem; color: var(--primary); margin: 32px 0 16px; }
.content-block h3 { font-size: 1.2rem; color: var(--text-primary); margin: 24px 0 12px; }
.content-block p { margin-bottom: 16px; color: var(--text-secondary); }
.content-block ul, .content-block ol { margin: 0 0 16px 24px; color: var(--text-secondary); }
.content-block li { margin-bottom: 8px; }

/* Features Detail */
.feature-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 48px;
    align-items: center;
    margin-bottom: 64px;
}

.feature-row:nth-child(even) .feature-visual { order: -1; }

.feature-content h3 {
    font-size: 1.5rem;
    color: var(--text-primary);
    margin-bottom: 16px;
}

.feature-content p {
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.feature-visual {
    background: var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 240px;
}

.feature-visual svg { max-width: 100%; color: var(--primary); }

/* 404 Page */
.error-page {
    min-height: 80vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 40px 24px;
}

.error-code {
    font-size: 8rem;
    font-weight: 800;
    color: var(--primary);
    line-height: 1;
    margin-bottom: 16px;
}

.error-msg {
    font-size: 1.3rem;
    color: var(--text-secondary);
    margin-bottom: 32px;
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 { font-size: 2rem; }
    .hero { padding: 56px 0; }
    .section { padding: 48px 0; }
    .footer-grid { grid-template-columns: 1fr; gap: 24px; }
    .feature-row { grid-template-columns: 1fr; gap: 24px; }
    .feature-row:nth-child(even) .feature-visual { order: 0; }
    
    .main-nav {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        background: var(--primary);
        flex-direction: column;
        padding: 16px;
        border-top: 1px solid rgba(255,255,255,0.1);
    }
    
    .main-nav.active { display: flex; }
    .nav-toggle { display: block; }
    
    .card-grid { grid-template-columns: 1fr; }
    .download-grid { grid-template-columns: 1fr; }
}