:root {
    --canvas-bg: #0b0e14;
    --surface-bg: rgba(18, 22, 28, 0.82);
    --surface-border: rgba(255, 255, 255, 0.08);
    --stroke-color: rgba(255, 255, 255, 0.06);
    --accent-glow: linear-gradient(135deg, rgba(99, 102, 241, 0.25) 0%, rgba(6, 182, 212, 0.18) 100%);
    --text-main: #eef2f6;
    --text-muted: #94a3b8;
    --text-accent: #38bdf8;
    --brand-gradient: linear-gradient(135deg, #6366f1 0%, #06b6d4 50%, #a855f7 100%);
    --card-radius: 20px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--canvas-bg);
    color: var(--text-main);
    line-height: 1.7;
    overflow-x: hidden;
    position: relative;
}

body::before,
body::after {
    content: "";
    position: fixed;
    z-index: -1;
    pointer-events: none;
    border-radius: 50%;
}
body::before {
    top: -10%;
    left: -6%;
    width: 58vw;
    height: 58vw;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.18) 0%, rgba(11, 14, 20, 0) 70%);
}
body::after {
    bottom: -6%;
    right: -6%;
    width: 48vw;
    height: 48vw;
    background: radial-gradient(circle, rgba(6, 182, 212, 0.13) 0%, rgba(11, 14, 20, 0) 70%);
}

/* 导航栏 */
.navbar {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: rgba(11, 14, 20, 0.82);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
    height: 72px;
    animation: fadeIn 0.7s ease both;
}
.navbar-container {
    max-width: 1400px;
    margin: 0 auto;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 48px;
}
.nav-brand a {
    text-decoration: none;
    color: var(--text-main);
    font-size: 19px;
    font-weight: 800;
    display: flex;
    align-items: center;
    gap: 10px;
    letter-spacing: -0.4px;
}
.nav-brand img { width: 30px; height: 30px; object-fit: contain; }
.nav-right-zone { display: flex; align-items: center; gap: 20px; }
.nav-menu { display: flex; gap: 4px; }
.nav-item {
    text-decoration: none;
    color: var(--text-muted);
    font-size: 13.5px;
    font-weight: 600;
    padding: 7px 16px;
    border-radius: 9px;
    transition: all 0.25s;
}
.nav-item:hover { color: var(--text-accent); background: rgba(56, 189, 248, 0.08); }
.nav-item.active { color: #fff; background: #1e293b; box-shadow: 0 3px 10px rgba(0, 0, 0, 0.3); }
.btn-github {
    display: inline-flex;
    align-items: center;
    gap: 7px;
    padding: 7px 15px;
    border-radius: 9px;
    background: #1e293b;
    border: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--text-main);
    text-decoration: none;
    font-size: 13px;
    font-weight: 600;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
    transition: all 0.25s;
}
.btn-github:hover { background: #334155; border-color: rgba(255, 255, 255, 0.18); transform: translateY(-1px); }
.btn-github svg { width: 15px; height: 15px; fill: currentColor; }

/* 按钮系统 */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 13px 28px;
    border-radius: 11px;
    font-size: 14.5px;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s;
    white-space: nowrap;
}
.btn-primary { background: var(--brand-gradient); color: #fff; box-shadow: 0 7px 26px rgba(99, 102, 241, 0.4); }
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 11px 32px rgba(99, 102, 241, 0.55); }
.btn-secondary { background: #1e293b; color: var(--text-main); border: 1px solid rgba(255, 255, 255, 0.1); box-shadow: 0 3px 16px rgba(0, 0, 0, 0.3); }
.btn-secondary:hover { background: #334155; transform: translateY(-2px); }

/* 通用标题 */
.section-header { text-align: center; margin-bottom: 48px; }
.section-eyebrow { font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: 1.6px; color: var(--text-accent); margin-bottom: 10px; display: block; }
.section-title { font-size: 34px; font-weight: 900; letter-spacing: -1px; color: var(--text-main); margin-bottom: 14px; }
.section-desc { font-size: 15px; color: var(--text-muted); max-width: 680px; margin: 0 auto; line-height: 1.7; }

/* 关于页 Hero */
.about-hero { padding: 48px 48px 0; text-align: center; max-width: 1400px; margin: 0 auto; }
.about-hero .hero-title { font-size: 42px; background: linear-gradient(135deg, #eef2f6 20%, #6366f1 50%, #06b6d4 100%); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; margin-bottom: 12px; }
.about-hero .hero-subtitle { font-size: 16px; max-width: 700px; margin: 0 auto 32px; color: var(--text-muted); line-height: 1.7; }

/* 使命宣言 */
.mission-statement {
    max-width: 800px;
    margin: 0 auto 80px;
    padding: 0 48px;
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    border: 1px solid rgba(99,102,241,0.25);
    border-radius: 24px;
    padding: 40px 32px;
    text-align: center;
}
.mission-statement h2 { font-size: 28px; font-weight: 900; color: var(--text-main); margin-bottom: 16px; }
.mission-statement p { font-size: 15px; color: var(--text-muted); line-height: 1.7; max-width: 600px; margin: 0 auto; }

/* 网站导航卡片 */
.site-map { max-width: 1000px; margin: 0 auto 80px; padding: 0 48px; display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 24px; }
.site-map-card { background: #1e293b; border: 1px solid rgba(255,255,255,0.06); border-radius: var(--card-radius); padding: 28px 20px; text-align: center; box-shadow: 0 6px 20px rgba(0,0,0,0.4); transition: transform 0.3s; }
.site-map-card:hover { transform: translateY(-5px); }
.site-map-icon { width: 48px; height: 48px; border-radius: 14px; background: rgba(99,102,241,0.15); display: flex; align-items: center; justify-content: center; margin: 0 auto 12px; color: var(--text-accent); }
.site-map-card h3 { font-size: 18px; font-weight: 800; color: var(--text-main); margin-bottom: 8px; }
.site-map-card p { font-size: 13px; color: var(--text-muted); line-height: 1.5; }

/* 时间线 */
.timeline { max-width: 800px; margin: 0 auto 80px; padding: 0 48px; position: relative; }
.timeline::before { content: ""; position: absolute; left: 40px; top: 0; bottom: 0; width: 2px; background: rgba(99,102,241,0.3); }
.timeline-item { display: flex; gap: 28px; margin-bottom: 32px; position: relative; }
.timeline-dot { width: 12px; height: 12px; background: var(--text-accent); border-radius: 50%; margin-top: 6px; flex-shrink: 0; z-index: 1; }
.timeline-content h3 { font-size: 16px; font-weight: 800; color: var(--text-main); margin-bottom: 4px; }
.timeline-content p { font-size: 13.5px; color: var(--text-muted); line-height: 1.6; }

/* 底部 CTA */
.bottom-cta { max-width: 1400px; margin: 0 auto 100px; padding: 0 48px; text-align: center; }
.cta-bottom-title { font-size: 30px; font-weight: 900; letter-spacing: -0.8px; color: var(--text-main); margin-bottom: 12px; }
.cta-bottom-text { font-size: 15px; color: var(--text-muted); margin-bottom: 28px; }
.cta-group { display: flex; align-items: center; justify-content: center; gap: 14px; flex-wrap: wrap; }

/* 页脚 */
.footer { background-color: #0f172a; color: var(--text-muted); padding: 64px 48px; border-top: 1px solid rgba(255,255,255,0.05); }
.footer-container { max-width: 1400px; margin: 0 auto; display: grid; grid-template-columns: 1.6fr 1fr 1fr; gap: 52px; }
.footer-brand-side { display: flex; flex-direction: column; gap: 14px; }
.footer-brand-title { font-size: 15px; font-weight: 800; color: var(--text-main); }
.footer-text { font-size: 12.5px; color: var(--text-muted); line-height: 1.6; }
.footer-nav-col { display: flex; flex-direction: column; gap: 14px; }
.footer-col-title { font-size: 13px; font-weight: 700; color: var(--text-main); letter-spacing: 0.4px; }
.footer-links-list { display: flex; flex-direction: column; gap: 10px; list-style: none; }
.footer-links-list a { color: var(--text-muted); text-decoration: none; font-size: 12.5px; font-weight: 500; transition: color 0.2s; }
.footer-links-list a:hover { color: var(--text-accent); }

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

/* 响应式 */
@media (max-width: 1024px) {
    .section-title { font-size: 28px; }
    .footer-container { grid-template-columns: 1fr 1fr; gap: 36px; }
}
@media (max-width: 768px) {
    .navbar-container { padding: 0 20px; }
    .nav-menu { display: none; }
    .about-hero { padding: 32px 20px 0; }
    .about-hero .hero-title { font-size: 30px; }
    .mission-statement { padding: 28px 20px; }
    .site-map { padding: 0 20px; }
    .timeline { padding: 0 20px; }
    .timeline::before { left: 24px; }
    .timeline-item { gap: 16px; }
    .bottom-cta { padding: 0 20px; margin-bottom: 60px; }
    .footer-container { grid-template-columns: 1fr; gap: 28px; }
    .footer { padding: 48px 24px; }
}