/* ===== LingFlow Design System Tokens ===== */
:root {
  --bg:            oklch(98% 0.005 245);
  --surface:       oklch(100% 0 0);
  --surface-raised:oklch(97% 0.008 245);
  --fg:            oklch(18% 0.02 250);
  --muted:         oklch(48% 0.018 250);
  --border:        oklch(90% 0.008 245);
  --primary:       oklch(52% 0.16 240);
  --primary-hover: oklch(48% 0.17 240);
  --primary-ghost: oklch(52% 0.16 240 / 0.08);
  --accent:        oklch(62% 0.14 195);
  --accent-ghost:  oklch(62% 0.14 195 / 0.10);
  --success:       oklch(58% 0.16 160);
  --success-ghost: oklch(58% 0.16 160 / 0.10);
  --warning:       oklch(65% 0.14 85);
  --warning-ghost: oklch(65% 0.14 85 / 0.10);
  --danger:        oklch(52% 0.18 25);
  --danger-ghost:  oklch(52% 0.18 25 / 0.08);
  --radius-sm: 6px; --radius-md: 10px; --radius-lg: 16px; --radius-xl: 24px; --radius-full: 9999px;
  --shadow-sm: 0 1px 2px oklch(0% 0 0 / 0.04);
  --shadow-md: 0 4px 12px oklch(0% 0 0 / 0.06);
  --shadow-lg: 0 8px 24px oklch(0% 0 0 / 0.08);
  --shadow-xl: 0 16px 48px oklch(0% 0 0 / 0.12);
  --font-sans: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Segoe UI', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Cascadia Code', ui-monospace, 'SF Mono', Menlo, monospace;
  --transition-fast: 150ms ease; --transition-base: 250ms ease; --transition-slow: 500ms cubic-bezier(0.4, 0, 0.2, 1);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; -webkit-font-smoothing: antialiased; scroll-behavior: smooth; }
body { font-family: var(--font-sans); background: var(--bg); color: var(--fg); line-height: 1.6; }

/* ===== Nav ===== */
.nav { position: fixed; top: 0; left: 0; right: 0; z-index: 100; background: oklch(98% 0.005 245 / 0.72); backdrop-filter: blur(16px) saturate(180%); -webkit-backdrop-filter: blur(16px) saturate(180%); border-bottom: 1px solid var(--border); transition: all var(--transition-base); }
.nav-inner { max-width: 1200px; margin: 0 auto; display: flex; align-items: center; justify-content: space-between; padding: 0 24px; height: 56px; }
.nav-brand { display: flex; align-items: center; gap: 10px; font-weight: 650; font-size: 16px; letter-spacing: -0.01em; text-decoration: none; color: var(--fg); }
.brand-icon { width: 28px; height: 28px; display: block; border-radius: var(--radius-sm); }
.nav-links { display: flex; align-items: center; gap: 6px; }
.nav-link { padding: 8px 14px; font-size: 13.5px; font-weight: 500; color: var(--muted); text-decoration: none; border-radius: var(--radius-md); transition: all var(--transition-fast); }
.nav-link:hover { color: var(--fg); background: var(--primary-ghost); }
.nav-cta { padding: 8px 20px; font-size: 13.5px; font-weight: 600; color: white; background: var(--primary); border-radius: var(--radius-md); text-decoration: none; transition: all var(--transition-fast); }
.nav-cta:hover { background: var(--primary-hover); box-shadow: 0 4px 16px oklch(52% 0.16 240 / 0.3); }

/* ===== Section ===== */
.section { padding: 96px 24px; }
.section-surface { background: var(--surface); }
.section-inner { max-width: 1200px; margin: 0 auto; }
.section-centered { text-align: center; }
.section-centered .section-label { margin: 0 auto 12px; }
.section-centered .section-title { margin: 0 auto 16px; }
.section-centered .section-desc { margin: 0 auto 48px; }
.section-label { font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; color: var(--primary); margin-bottom: 12px; }
.section-title { font-size: clamp(28px, 4vw, 40px); font-weight: 700; letter-spacing: -0.03em; line-height: 1.2; margin-bottom: 16px; }
.section-desc { font-size: 17px; color: var(--muted); line-height: 1.7; max-width: 640px; }

/* ===== Hero ===== */
.hero { padding: 160px 24px 120px; text-align: center; position: relative; overflow: hidden; }
.hero::before { content: ''; position: absolute; top: -50%; left: -50%; width: 200%; height: 200%; background: radial-gradient(ellipse at 50% 40%, oklch(62% 0.14 195 / 0.06) 0%, transparent 60%), radial-gradient(ellipse at 50% 60%, oklch(52% 0.16 240 / 0.04) 0%, transparent 50%); pointer-events: none; }
.hero-inner { max-width: 720px; margin: 0 auto; position: relative; z-index: 1; }
.hero-icon { width: 96px; height: 96px; display: block; margin: 0 auto 36px; border-radius: var(--radius-xl); box-shadow: 0 0 60px oklch(52% 0.16 240 / 0.25), 0 0 120px oklch(52% 0.16 240 / 0.10); animation: orb-breathe 3s ease-in-out infinite; }
@keyframes orb-breathe { 0%, 100% { transform: scale(1); } 50% { transform: scale(1.06); } }
.hero h1 { font-size: clamp(36px, 6vw, 56px); font-weight: 750; letter-spacing: -0.04em; line-height: 1.1; margin-bottom: 20px; }
.hero h1 span { background: linear-gradient(135deg, var(--primary), var(--accent)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.hero p { font-size: 18px; color: var(--muted); line-height: 1.7; max-width: 560px; margin: 0 auto 32px; }
.hero-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 12px 28px; border-radius: var(--radius-md); font-size: 15px; font-weight: 600; font-family: inherit; cursor: pointer; text-decoration: none; transition: all var(--transition-fast); border: 1px solid transparent; }
.btn-primary { background: var(--primary); color: white; border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-hover); box-shadow: 0 6px 20px oklch(52% 0.16 240 / 0.3); transform: translateY(-1px); }
.btn-outline { background: transparent; color: var(--fg); border-color: var(--border); }
.btn-outline:hover { border-color: var(--primary); background: var(--primary-ghost); }
.btn svg { width: 18px; height: 18px; }

/* ===== Feature Grid ===== */
.feature-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 20px; margin-top: 48px; }
.feature-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg); padding: 32px 28px; transition: all var(--transition-base); }
.feature-card:hover { border-color: var(--primary); box-shadow: var(--shadow-lg); transform: translateY(-2px); }
.feature-icon { width: 44px; height: 44px; border-radius: var(--radius-md); background: var(--primary-ghost); color: var(--primary); display: flex; align-items: center; justify-content: center; margin-bottom: 20px; }
.feature-icon svg { width: 22px; height: 22px; }
.feature-card h3 { font-size: 17px; font-weight: 650; letter-spacing: -0.01em; margin-bottom: 8px; }
.feature-card p { font-size: 14px; color: var(--muted); line-height: 1.65; }

/* ===== Platform Cards ===== */
.platform-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 20px; margin-top: 48px; }
.platform-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-xl); overflow: hidden; transition: all var(--transition-base); }
.platform-card:hover { border-color: var(--primary); box-shadow: var(--shadow-lg); }
.platform-top { padding: 28px 28px 0; }
.platform-icon { width: 48px; height: 48px; border-radius: var(--radius-lg); display: flex; align-items: center; justify-content: center; margin-bottom: 16px; }
.platform-icon.desktop { background: oklch(52% 0.16 240 / 0.1); color: var(--primary); }
.platform-icon.extension { background: oklch(62% 0.14 195 / 0.1); color: var(--accent); }
.platform-icon.mobile { background: oklch(58% 0.16 160 / 0.1); color: var(--success); }
.platform-icon svg { width: 24px; height: 24px; }
.platform-card h3 { font-size: 20px; font-weight: 650; letter-spacing: -0.02em; margin-bottom: 6px; }
.platform-tag { display: inline-flex; align-items: center; gap: 4px; font-size: 12px; color: var(--muted); margin-bottom: 16px; }
.platform-card ul { list-style: none; padding: 0; margin: 0; border-top: 1px solid var(--border); }
.platform-card li { display: flex; align-items: center; gap: 10px; padding: 14px 28px; font-size: 13.5px; border-bottom: 1px solid var(--border); }
.platform-card li:last-child { border-bottom: none; }
.platform-card li svg { width: 16px; height: 16px; color: var(--success); flex-shrink: 0; }

/* ===== Provider Section ===== */
.provider-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 12px; margin-top: 48px; }
.provider-chip { display: flex; align-items: center; gap: 10px; padding: 16px 20px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg); font-size: 14px; font-weight: 550; transition: all var(--transition-fast); }
.provider-chip:hover { border-color: var(--primary); background: var(--primary-ghost); }
.provider-chip-dot { width: 10px; height: 10px; border-radius: 50%; flex-shrink: 0; }
.provider-chip-dot.free { background: var(--muted); }
.provider-chip-dot.ai { background: var(--accent); }
.provider-chip-dot.mock { background: var(--border); border: 1.5px dashed var(--muted); }
.provider-chip-tag { margin-left: auto; font-size: 10px; font-weight: 600; padding: 2px 8px; border-radius: var(--radius-full); text-transform: uppercase; letter-spacing: 0.04em; }
.provider-chip-tag.free-tag { background: var(--surface-raised); color: var(--muted); }
.provider-chip-tag.ai-tag { background: var(--accent-ghost); color: var(--accent); }
.provider-note { margin-top: 24px; color: var(--muted); font-size: 13px; text-align: center; }

/* ===== Privacy Section ===== */
.privacy-banner { background: var(--surface); border: 1px solid var(--success); border-radius: var(--radius-xl); padding: 40px 36px; margin-top: 48px; position: relative; overflow: hidden; }
.privacy-banner::before { content: ''; position: absolute; inset: 0; background: radial-gradient(ellipse at 80% 50%, oklch(58% 0.16 160 / 0.06), transparent 60%); pointer-events: none; }
.privacy-banner-inner { position: relative; z-index: 1; display: grid; grid-template-columns: 1fr 1fr; gap: 32px; align-items: center; }
.privacy-banner h3 { font-size: 24px; font-weight: 650; letter-spacing: -0.02em; margin-bottom: 12px; }
.privacy-banner p { font-size: 14px; color: var(--muted); line-height: 1.7; margin-bottom: 16px; }
.privacy-items { display: flex; flex-direction: column; gap: 12px; }
.privacy-item { display: flex; align-items: center; gap: 10px; font-size: 13.5px; font-weight: 500; }
.privacy-item svg { width: 18px; height: 18px; color: var(--success); flex-shrink: 0; }

/* ===== Getting Started ===== */
.steps { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 20px; margin-top: 48px; }
.step-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg); padding: 28px; position: relative; }
.step-num { font-family: var(--font-mono); font-size: 40px; font-weight: 700; color: var(--primary-ghost); color: oklch(52% 0.16 240 / 0.15); line-height: 1; margin-bottom: 12px; }
.step-card h4 { font-size: 16px; font-weight: 650; margin-bottom: 8px; }
.step-card p { font-size: 13.5px; color: var(--muted); line-height: 1.6; }
.step-card code { font-family: var(--font-mono); font-size: 12px; padding: 3px 8px; border-radius: var(--radius-sm); background: var(--bg); border: 1px solid var(--border); color: var(--fg); word-break: break-all; }

/* ===== Architecture Diagram ===== */
.arch-diagram { margin-top: 48px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-xl); padding: 40px 32px; display: flex; align-items: flex-start; justify-content: center; gap: 24px; flex-wrap: wrap; }
.arch-node { display: flex; flex-direction: column; align-items: center; gap: 8px; }
.arch-node-box { padding: 16px 24px; border-radius: var(--radius-lg); font-size: 14px; font-weight: 600; text-align: center; }
.arch-node-box.desktop-box { background: var(--primary-ghost); color: var(--primary); border: 1.5px solid oklch(52% 0.16 240 / 0.2); }
.arch-node-box.extension-box { background: var(--accent-ghost); color: var(--accent); border: 1.5px solid oklch(62% 0.14 195 / 0.2); }
.arch-node-box.browser-box { background: var(--success-ghost); color: var(--success); border: 1.5px solid oklch(58% 0.16 160 / 0.2); }
.arch-node-label { font-size: 11px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; font-weight: 600; }
.arch-arrow { height: 56px; display: flex; align-items: center; justify-content: center; font-size: 24px; line-height: 1; color: var(--muted); flex-shrink: 0; }
.arch-note { margin-top: 24px; color: var(--muted); font-size: 13px; }
.inline-code { padding: 2px 8px; border: 1px solid var(--border); border-radius: var(--radius-sm); background: var(--bg); color: var(--fg); font-family: var(--font-mono); font-size: 12px; }

/* ===== Links and utility blocks ===== */
.text-link { color: var(--primary); }
.muted-link { color: var(--muted); }
.start-cta { margin-top: 48px; text-align: center; }

/* ===== Footer ===== */
.footer { border-top: 1px solid var(--border); padding: 48px 24px 32px; background: var(--surface); }
.footer-inner { max-width: 1200px; margin: 0 auto; display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; }
.footer-brand { display: flex; align-items: center; gap: 10px; font-weight: 650; font-size: 16px; margin-bottom: 12px; }
.footer-icon { width: 24px; height: 24px; display: block; border-radius: var(--radius-sm); }
.footer-desc { font-size: 13px; color: var(--muted); line-height: 1.7; }
.footer-col h4 { font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); margin-bottom: 16px; }
.footer-col a { display: block; font-size: 13.5px; color: var(--fg); text-decoration: none; margin-bottom: 10px; transition: color var(--transition-fast); }
.footer-col a:hover { color: var(--primary); }
.footer-bottom { max-width: 1200px; margin: 32px auto 0; padding-top: 24px; border-top: 1px solid var(--border); display: flex; align-items: center; justify-content: space-between; font-size: 12px; color: var(--muted); flex-wrap: wrap; gap: 12px; }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero { padding: 120px 20px 80px; }
  .hero h1 { font-size: 32px; }
  .hero p { font-size: 16px; }
  .section { padding: 64px 20px; }
  .feature-grid { grid-template-columns: 1fr; }
  .platform-grid { grid-template-columns: 1fr; }
  .privacy-banner-inner { grid-template-columns: 1fr; }
  .arch-diagram { flex-direction: column; flex-wrap: nowrap; align-items: center; gap: 12px; }
  .arch-node,
  .arch-arrow { width: 160px; }
  .arch-arrow { height: 24px; align-self: center; transform: rotate(90deg); }
  .footer-inner { grid-template-columns: 1fr 1fr; gap: 32px; }
  .nav-links { display: none; }
  .steps { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
  .footer-inner { grid-template-columns: 1fr; }
  .hero-actions { flex-direction: column; align-items: center; }
  .btn { width: 100%; justify-content: center; }
}