:root {
  --blue-50: #eff6ff;
  --blue-100: #dbeafe;
  --blue-200: #bfdbfe;
  --blue-500: #3b82f6;
  --blue-600: #2563eb;
  --blue-700: #1d4ed8;
  --blue-800: #1e3a5f;
  --blue-900: #0f1b2d;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;
  --white: #ffffff;
  --shell: min(1100px, calc(100vw - 32px));
  --radius: 12px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
  --font: -apple-system, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", sans-serif;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { font-family: var(--font); color: var(--gray-800); background: var(--gray-50); line-height: 1.6; -webkit-font-smoothing: antialiased; }
a { color: var(--blue-600); text-decoration: none; }
a:hover { text-decoration: underline; }
.shell { width: var(--shell); margin: 0 auto; }
.nav { background: var(--white); border-bottom: 1px solid var(--gray-200); position: sticky; top: 0; z-index: 50; }
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 60px; }
.nav-logo { font-size: 20px; font-weight: 700; color: var(--blue-800); letter-spacing: -0.3px; }
.nav-logo span { color: var(--blue-600); }
.nav-links { display: flex; gap: 24px; align-items: center; }
.nav-links a { font-size: 14px; color: var(--gray-600); font-weight: 500; }
.nav-links a:hover { color: var(--blue-600); text-decoration: none; }
.nav-btn { display: inline-block; padding: 8px 20px; border-radius: 8px; background: var(--blue-600); color: var(--white) !important; font-weight: 600; font-size: 14px; transition: background 0.2s; }
.nav-btn:hover { background: var(--blue-700); text-decoration: none; }
.hero { text-align: center; padding: 80px 0 60px; background: linear-gradient(135deg, var(--blue-900) 0%, var(--blue-800) 50%, #1a365d 100%); color: var(--white); }
.hero h1 { font-size: clamp(28px, 4vw, 48px); font-weight: 700; line-height: 1.3; margin-bottom: 16px; }
.hero p { font-size: clamp(16px, 2vw, 20px); opacity: 0.85; max-width: 600px; margin: 0 auto 32px; line-height: 1.7; }
.hero-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.hero-btn { display: inline-flex; align-items: center; gap: 8px; padding: 14px 32px; border-radius: var(--radius); font-size: 16px; font-weight: 600; transition: all 0.2s; }
.hero-btn-primary { background: var(--white); color: var(--blue-800); }
.hero-btn-primary:hover { background: var(--gray-100); text-decoration: none; }
.hero-btn-secondary { background: rgba(255,255,255,0.15); color: var(--white); border: 1px solid rgba(255,255,255,0.25); }
.hero-btn-secondary:hover { background: rgba(255,255,255,0.2); text-decoration: none; }
.hero-stats { display: flex; gap: 40px; justify-content: center; margin-top: 40px; flex-wrap: wrap; }
.hero-stat { text-align: center; }
.hero-stat-num { font-size: 28px; font-weight: 700; }
.hero-stat-label { font-size: 13px; opacity: 0.7; margin-top: 4px; }
.section { padding: 60px 0; }
.section-title { text-align: center; font-size: clamp(22px, 3vw, 32px); font-weight: 700; color: var(--gray-900); margin-bottom: 12px; }
.section-subtitle { text-align: center; font-size: 16px; color: var(--gray-500); max-width: 500px; margin: 0 auto 40px; }
.value-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 24px; }
.value-card { background: var(--white); border-radius: var(--radius); padding: 32px 24px; box-shadow: var(--shadow-sm); border: 1px solid var(--gray-100); transition: box-shadow 0.2s; }
.value-card:hover { box-shadow: var(--shadow-md); }
.value-card h3 { font-size: 17px; font-weight: 600; margin-bottom: 8px; color: var(--gray-900); }
.value-card p { font-size: 14px; color: var(--gray-600); line-height: 1.7; }
.value-badge { display: inline-block; font-size: 11px; font-weight: 600; padding: 3px 8px; border-radius: 4px; margin-bottom: 12px; }
.badge-data { background: #dcfce7; color: #15803d; }
.badge-ai { background: #dbeafe; color: #1d4ed8; }
.compare-section { background: var(--white); border-top: 1px solid var(--gray-200); }
.compare-table { width: 100%; border-collapse: collapse; font-size: 14px; }
.compare-table th, .compare-table td { padding: 14px 16px; text-align: left; border-bottom: 1px solid var(--gray-100); }
.compare-table th { font-weight: 600; color: var(--gray-500); font-size: 12px; text-transform: uppercase; letter-spacing: 0.5px; }
.compare-table td:first-child { font-weight: 600; color: var(--gray-800); }
.compare-check { color: #16a34a; font-weight: 700; }
.compare-cross { color: var(--gray-400); }
.pricing-card { background: var(--white); border-radius: var(--radius); padding: 40px 32px; box-shadow: var(--shadow-md); text-align: center; border: 2px solid var(--blue-100); max-width: 400px; margin: 0 auto; }
.pricing-card.premium { border-color: var(--blue-500); }
.pricing-price { font-size: 48px; font-weight: 700; color: var(--blue-800); margin: 16px 0; }
.pricing-price span { font-size: 20px; font-weight: 400; color: var(--gray-500); }
.pricing-desc { font-size: 14px; color: var(--gray-500); margin-bottom: 24px; }
.pricing-features { list-style: none; text-align: left; margin: 24px 0; }
.pricing-features li { padding: 8px 0; font-size: 14px; color: var(--gray-700); display: flex; gap: 10px; }
.pricing-features li::before { content: ""; color: var(--blue-600); font-weight: 700; }
.pricing-btn { display: block; width: 100%; padding: 14px; border-radius: var(--radius); background: var(--blue-600); color: var(--white); font-size: 16px; font-weight: 600; border: none; cursor: pointer; transition: background 0.2s; }
.pricing-btn:hover { background: var(--blue-700); }
.footer { border-top: 1px solid var(--gray-200); padding: 32px 0; text-align: center; font-size: 13px; color: var(--gray-400); }
.tools-section { background: var(--white); border-top: 1px solid var(--gray-200); }
.tools-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 16px; }
.tool-entry { display: block; background: var(--white); border: 1px solid var(--gray-200); border-radius: 8px; padding: 20px; transition: box-shadow 0.2s, border-color 0.2s; color: inherit; }
.tool-entry:hover { box-shadow: var(--shadow-md); border-color: var(--blue-500); text-decoration: none; }
.tool-entry .tool-num { font-size: 12px; font-weight: 700; color: var(--blue-600); }
.tool-entry h3 { font-size: 16px; font-weight: 700; color: var(--gray-900); margin: 8px 0 6px; }
.tool-entry p { font-size: 13px; color: var(--gray-500); line-height: 1.7; }
/* 导航栏登录/注册按钮 */
.nav-btn-outline { display: inline-block; padding: 8px 20px; border-radius: 8px; background: transparent; color: var(--blue-600) !important; border: 1px solid var(--blue-600); font-weight: 600; font-size: 14px; transition: all 0.2s; }
.nav-btn-outline:hover { background: var(--blue-50); text-decoration: none; }
.nav-user { font-size: 13px; color: var(--gray-700); font-weight: 500; display: inline-flex; align-items: center; gap: 6px; }
.nav-user-avatar { width: 28px; height: 28px; border-radius: 50%; background: var(--blue-600); color: var(--white); display: inline-flex; align-items: center; justify-content: center; font-size: 13px; font-weight: 600; }
/* 聊天历史面板 */
.history-toggle { cursor: pointer; font-size: 14px; color: var(--blue-600); font-weight: 500; padding: 6px 12px; border-radius: 8px; border: 1px solid var(--gray-200); background: var(--white); transition: all 0.2s; }
.history-toggle:hover { border-color: var(--blue-500); background: var(--blue-50); }
.history-toggle.active { background: var(--blue-50); border-color: var(--blue-500); }
.history-panel { background: var(--white); border: 1px solid var(--gray-200); border-radius: var(--radius); margin-bottom: 16px; max-height: 360px; overflow-y: auto; display: none; }
.history-panel.open { display: block; }
.history-item { padding: 14px 18px; border-bottom: 1px solid var(--gray-100); cursor: pointer; transition: background 0.15s; display: flex; gap: 12px; align-items: flex-start; }
.history-item:hover { background: var(--gray-50); }
.history-item:last-child { border-bottom: none; }
.history-item.active { background: var(--blue-50); border-left: 3px solid var(--blue-500); }
.history-item-date { font-size: 12px; color: var(--gray-400); white-space: nowrap; min-width: 80px; padding-top: 2px; }
.history-item-q { font-size: 14px; color: var(--gray-700); line-height: 1.5; flex: 1; }
.history-item-preview { font-size: 12px; color: var(--gray-400); margin-top: 3px; }
.history-empty { text-align: center; padding: 32px 20px; color: var(--gray-400); font-size: 14px; }
.history-load-more { text-align: center; padding: 12px; }
.history-load-more button { font-size: 13px; color: var(--blue-600); background: none; border: none; cursor: pointer; padding: 6px 16px; }
.history-load-more button:hover { text-decoration: underline; }
/* 游客注册引导遮罩 */
.guest-overlay { display: none; position: fixed; inset: 0; background: rgba(15,27,45,0.7); z-index: 100; align-items: center; justify-content: center; }
.guest-overlay.open { display: flex; }
.guest-dialog { background: var(--white); border-radius: var(--radius); padding: 40px 32px; max-width: 400px; width: calc(100vw - 40px); text-align: center; box-shadow: var(--shadow-lg); }
.guest-dialog h3 { font-size: 20px; margin-bottom: 8px; color: var(--gray-900); }
.guest-dialog p { font-size: 14px; color: var(--gray-500); margin-bottom: 24px; line-height: 1.7; }
.guest-dialog .hero-btn-primary { background: var(--blue-600); color: var(--white); display: block; margin-bottom: 10px; text-align: center; }
.guest-dialog .guest-login-link { font-size: 13px; color: var(--blue-600); cursor: pointer; background: none; border: none; }
.guest-dialog .guest-login-link:hover { text-decoration: underline; }
@media (max-width: 768px) {
  .nav-links a:not(.nav-btn):not(.nav-btn-outline) { display: none; }
  .hero { padding: 48px 0 40px; }
  .section { padding: 40px 0; }
  .value-grid { grid-template-columns: 1fr; }
  .compare-table { font-size: 12px; }
  .compare-table th, .compare-table td { padding: 10px 8px; }
  .pricing-card { max-width: 100%; }
  .history-item { flex-direction: column; gap: 4px; }
  .history-item-date { min-width: auto; }
}