/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-font-smoothing: antialiased; }
body {
    font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Microsoft YaHei", sans-serif;
    color: #1d1d1f; background: #fff; line-height: 1.5; font-size: 17px;
}
img { max-width: 100%; height: auto; display: block; }
a { color: #0066cc; text-decoration: none; }
a:hover { text-decoration: underline; }
ul { list-style: none; }
.container { max-width: 980px; margin: 0 auto; padding: 0 22px; }
.container-wide { max-width: 1400px; margin: 0 auto; padding: 0 22px; }

/* ===== Nav ===== */
.site-nav {
    position: sticky; top: 0; z-index: 100;
    background: rgba(255,255,255,0.88);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid #e8e8ed;
}
.nav-inner {
    max-width: 1024px; margin: 0 auto;
    display: flex; align-items: center; justify-content: space-between;
    height: 44px; padding: 0 22px;
}
.logo { color: #1d1d1f; font-size: 17px; font-weight: 600; }
.nav-inner nav ul { display: flex; gap: 28px; }
.nav-inner nav a { color: #1d1d1f; font-size: 12px; opacity: 0.8; }
.nav-inner nav a:hover { opacity: 1; text-decoration: none; }

/* ===== Hero ===== */
.hero {
    background: linear-gradient(135deg, #0f0c29 0%, #302b63 50%, #24243e 100%);
    color: #fff; text-align: center; padding: 80px 22px 0; overflow: hidden;
}
.hero h1 { font-size: 56px; font-weight: 700; letter-spacing: -0.02em; line-height: 1.07; margin-bottom: 14px; }
.hero .tagline {
    font-size: 24px; font-weight: 600;
    background: linear-gradient(90deg, #818cf8, #c084fc, #f472b6);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text; margin-bottom: 16px;
}
.hero .sub { font-size: 19px; color: #c7d2fe; max-width: 640px; margin: 0 auto 28px; line-height: 1.6; }
.cta-group { display: flex; gap: 16px; justify-content: center; margin-bottom: 50px; }
.btn {
    display: inline-block; padding: 12px 24px;
    border-radius: 980px; font-size: 17px; transition: all 0.2s;
}
.btn-primary { background: #6366f1; color: #fff; }
.btn-primary:hover { background: #4f46e5; text-decoration: none; }
.btn-secondary { color: #a5b4fc; }

/* ===== Sections ===== */
.section { padding: 100px 0; }
.section-gray { background: #f5f5f7; }
.section-dark { background: #0f0c29; color: #fff; }
.section h2 { font-size: 44px; font-weight: 700; text-align: center; letter-spacing: -0.02em; margin-bottom: 18px; }
.section .subtitle { font-size: 20px; text-align: center; color: #6e6e73; max-width: 680px; margin: 0 auto 50px; line-height: 1.5; }
.section-dark .subtitle { color: #94a3b8; }

/* ===== Feature Cards ===== */
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 40px; }
.feature-card { background: #fff; border-radius: 20px; padding: 32px; }
.section-dark .feature-card { background: #1e1b4b; }
.feature-card .icon {
    width: 44px; height: 44px; border-radius: 12px;
    background: linear-gradient(135deg, #6366f1, #8b5cf6);
    display: flex; align-items: center; justify-content: center;
    margin-bottom: 16px; font-size: 22px;
}
.feature-card h3 { font-size: 19px; font-weight: 600; margin-bottom: 8px; }
.feature-card p { font-size: 14px; color: #6e6e73; line-height: 1.6; }
.section-dark .feature-card p { color: #94a3b8; }

/* ===== FAQ Grid ===== */
.faq-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 40px; }
.faq-card {
    background: #fff; border: 1px solid #e8e8ed; border-radius: 16px;
    padding: 24px; transition: all 0.2s;
}
.faq-card:hover { box-shadow: 0 4px 20px rgba(99,102,241,0.12); border-color: #c7d2fe; text-decoration: none; }
.faq-card .num {
    font-size: 13px; color: #6366f1; font-weight: 600; margin-bottom: 8px;
}
.faq-card h3 { font-size: 16px; font-weight: 600; color: #1d1d1f; margin-bottom: 6px; line-height: 1.4; }
.faq-card p { font-size: 13px; color: #6e6e73; line-height: 1.5; }

/* ===== Article ===== */
.article-page { padding: 60px 0 100px; max-width: 720px; margin: 0 auto; }
.article-page h1 { font-size: 38px; font-weight: 700; letter-spacing: -0.02em; line-height: 1.25; margin-bottom: 16px; }
.article-page .meta {
    font-size: 14px; color: #86868b; margin-bottom: 40px;
    padding-bottom: 20px; border-bottom: 1px solid #e8e8ed;
}
.article-page h2 { font-size: 24px; font-weight: 700; margin: 36px 0 14px; }
.article-page p { font-size: 17px; line-height: 1.75; color: #1d1d1f; margin-bottom: 16px; }
.article-page ul { margin: 16px 0; padding-left: 22px; }
.article-page ul li { font-size: 16px; line-height: 1.9; color: #3a3a3c; list-style: disc; }
.article-page strong { color: #1d1d1f; }
.article-page .related {
    margin-top: 50px; padding: 28px;
    background: linear-gradient(135deg, #eef2ff, #f5f3ff);
    border-radius: 16px; border: 1px solid #e0e7ff;
}
.article-page .related h3 { font-size: 16px; font-weight: 600; margin-bottom: 12px; }
.article-page .related a { display: inline-block; margin: 4px 14px 4px 0; font-size: 15px; }

/* ===== 404 ===== */
.error-page {
    min-height: 70vh; display: flex; flex-direction: column;
    align-items: center; justify-content: center; text-align: center; padding: 40px 22px;
}
.error-page .code { font-size: 120px; font-weight: 700; line-height: 1; margin-bottom: 16px; color: #6366f1; }
.error-page h1 { font-size: 32px; font-weight: 700; margin-bottom: 12px; }
.error-page p { font-size: 17px; color: #6e6e73; max-width: 400px; margin-bottom: 30px; }

/* ===== Footer ===== */
.site-footer { background: #f5f5f7; padding: 40px 0; font-size: 12px; color: #86868b; line-height: 1.5; }
.footer-links {
    border-top: 1px solid #d2d2d7; padding-top: 20px; margin-top: 20px;
    display: flex; gap: 20px; flex-wrap: wrap;
}
.site-footer a { color: #515154; }

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .hero h1 { font-size: 36px; }
    .hero .tagline { font-size: 20px; }
    .section h2 { font-size: 30px; }
    .article-page h1 { font-size: 26px; }
    .feature-grid { grid-template-columns: 1fr; }
    .faq-grid { grid-template-columns: 1fr; }
    .nav-inner nav ul { gap: 14px; }
    .nav-inner nav a { font-size: 11px; }
}