/* ========================================================
   BiReader SEO Landing Pages — Shared CSS
   Identical base to index.html + SEO-page extras
   ======================================================== */

/* Light Theme */
:root,
[data-theme="light"] {
  --bg: #FEFCF9;
  --bg-soft: #F8F6F3;
  --bg-softer: #F0EDE8;
  --accent: #2563eb;
  --accent-soft: rgba(37, 99, 235, 0.08);
  --accent-strong: #1d4ed8;
  --accent-alt: #16a34a;
  --accent-warm: #f59e0b;
  --text-main: #1f2937;
  --text-soft: #4b5563;
  --text-muted: #6b7280;
  --border-soft: #e5e7eb;
  --border-medium: #d1d5db;
  --danger: #dc2626;
  --success: #16a34a;
  --shadow-soft: 0 10px 30px rgba(0, 0, 0, 0.08);
  --shadow-medium: 0 4px 12px rgba(0, 0, 0, 0.1);
  --gradient-hero: linear-gradient(135deg, #EFF6FF 0%, #FEF3C7 50%, #FEE2E2 100%);
  --gradient-card: linear-gradient(145deg, #ffffff, #fafaf9);
  --radius-xl: 18px;
  --radius-full: 999px;
  --max-width: 1120px;
}

/* Dark Theme */
[data-theme="dark"] {
  --bg: #0a0f1e;
  --bg-soft: #141b2e;
  --bg-softer: #1a2235;
  --accent: #60a5fa;
  --accent-soft: rgba(96, 165, 250, 0.12);
  --accent-strong: #3b82f6;
  --accent-alt: #34d399;
  --accent-warm: #fbbf24;
  --text-main: #f3f4f6;
  --text-soft: #d1d5db;
  --text-muted: #9ca3af;
  --border-soft: #374151;
  --border-medium: #4b5563;
  --danger: #f87171;
  --success: #34d399;
  --shadow-soft: 0 20px 40px rgba(0, 0, 0, 0.6);
  --shadow-medium: 0 8px 20px rgba(0, 0, 0, 0.4);
  --gradient-hero: radial-gradient(circle at top, #1e293b 0%, #0f172a 40%, #020617 80%);
  --gradient-card: linear-gradient(145deg, #0f172a, #1e293b);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "SF Pro Text", "Roboto", "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text-main);
  scroll-behavior: smooth;
  font-size: 16px;
  transition: background-color 0.3s ease, color 0.3s ease;
}

[data-theme="dark"] body { background: radial-gradient(circle at top, #1e293b 0%, #0f172a 40%, #020617 80%); }
[data-theme="light"] body { background: linear-gradient(180deg, #FEFCF9 0%, #FEF3C7 100%); }

body { display: flex; justify-content: center; }

.page {
  width: 100%;
  max-width: var(--max-width);
  padding: 24px 20px 60px;
}

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 32px;
}

.logo-link { text-decoration: none; color: inherit; display: inline-flex; align-items: center; gap: 10px; }
.logo { display: flex; align-items: center; gap: 10px; }
.logo-mark { width: 40px; height: 40px; border-radius: 10px; display: block; object-fit: contain; }
.logo-text-main { font-weight: 600; letter-spacing: 0.02em; }
.logo-text-sub { font-size: 13px; color: var(--text-muted); }

nav { display: flex; align-items: center; gap: 20px; font-size: 14px; }
nav a { text-decoration: none; color: var(--text-soft); padding: 4px 0; font-weight: 500; }
nav a.highlight-login { color: var(--accent-alt); font-weight: 600; }
nav a:hover { color: var(--text-main); }

.nav-cta {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 6px 14px; border-radius: 999px;
  background: var(--bg-soft); border: 1px solid var(--border-medium);
  color: var(--text-soft); font-size: 13px; text-decoration: none;
  transition: all 0.2s ease;
}
.nav-cta span { font-size: 11px; text-transform: uppercase; letter-spacing: 0.12em; color: var(--accent-alt); }
.nav-cta:hover { border-color: var(--accent); color: var(--text-main); background: var(--bg-softer); }

.theme-toggle {
  width: 40px; height: 40px; border-radius: 50%;
  background: var(--bg-soft); border: 1px solid var(--border-soft);
  display: flex; align-items: center; justify-content: center;
  cursor: pointer; transition: all 0.2s ease; padding: 0; font-size: 18px;
}
.theme-toggle:hover { background: var(--bg-softer); border-color: var(--accent); transform: rotate(20deg); }
.theme-toggle:active { transform: scale(0.95) rotate(20deg); }

section { margin-bottom: 52px; }

.section-title { font-size: 22px; margin-bottom: 8px; }
.section-subtitle { font-size: 16px; color: var(--text-muted); max-width: 520px; margin-bottom: 24px; }

.features-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; }
.feature-card { background: var(--bg-soft); border-radius: var(--radius-xl); padding: 16px; border: 1px solid var(--border-soft); }
.feature-icon { width: 26px; height: 26px; border-radius: 10px; background: var(--accent-soft); display: flex; align-items: center; justify-content: center; margin-bottom: 10px; font-size: 16px; }
.feature-title { font-size: 16px; margin-bottom: 6px; }
.feature-text { font-size: 15px; color: var(--text-soft); margin-bottom: 10px; }
.feature-tag { font-size: 11px; color: var(--accent-alt); text-transform: uppercase; letter-spacing: 0.1em; }

.faq-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.faq-item { background: var(--bg-soft); border-radius: 16px; padding: 12px 14px; border: 1px solid var(--border-soft); font-size: 15px; }
.faq-q { font-weight: 500; margin-bottom: 4px; }
.faq-a { color: var(--text-soft); }

.cta-final { text-align: center; padding: 20px 18px; border-radius: 20px; background: var(--gradient-card); border: 1px solid var(--border-soft); box-shadow: var(--shadow-soft); }
.cta-final h2 { margin: 0 0 4px; font-size: 20px; }
.cta-final p { margin: 0 0 14px; font-size: 16px; color: var(--text-soft); }

.btn-primary,
.btn-secondary {
  font-size: 14px; padding: 10px 18px; border-radius: var(--radius-full);
  text-decoration: none; display: inline-flex; align-items: center; justify-content: center;
  gap: 8px; border: none; cursor: pointer; white-space: nowrap;
  transition: transform 0.08s ease-out, box-shadow 0.08s ease-out;
}
.btn-primary { background: linear-gradient(135deg, var(--accent-alt) 0%, var(--success) 100%); color: #fff; font-weight: 600; box-shadow: var(--shadow-medium); border: 1px solid var(--accent-alt); }
.btn-primary:hover { transform: translateY(-2px); box-shadow: var(--shadow-soft); }
.btn-secondary { background: var(--bg-soft); color: var(--text-soft); border: 1px solid var(--border-medium); }
.btn-secondary:hover { background: var(--bg-softer); color: var(--text-main); transform: translateY(-1px); }

footer { margin-top: 32px; font-size: 11px; color: var(--text-muted); display: flex; justify-content: space-between; flex-wrap: wrap; gap: 8px; }
footer a { color: var(--text-muted); text-decoration: none; }
footer a:hover { color: var(--text-main); text-decoration: underline; }
footer .social-link { display: inline-flex; align-items: center; justify-content: center; width: 28px; height: 28px; border-radius: 50%; background: var(--bg-softer); border: 1px solid var(--border-soft); color: var(--text-muted); vertical-align: middle; transition: all 0.2s ease; }
footer .social-link:hover { color: var(--accent); border-color: var(--accent); background: var(--accent-soft); text-decoration: none; transform: translateY(-1px); }

/* =============================================
   SEO LANDING PAGE — Extra Styles
   ============================================= */

/* Breadcrumb */
.breadcrumb {
  display: flex; align-items: center; gap: 6px;
  font-size: 13px; color: var(--text-muted);
  margin-bottom: 24px; flex-wrap: wrap;
}
.breadcrumb a { color: var(--text-muted); text-decoration: none; }
.breadcrumb a:hover { color: var(--accent); text-decoration: underline; }
.breadcrumb-sep { color: var(--border-medium); }

/* Page hero for SEO pages */
.seo-hero {
  margin-bottom: 48px;
  padding: 32px 0 0;
}
.seo-hero h1 {
  font-size: clamp(28px, 4.5vw, 38px);
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin: 0 0 16px;
}
.level-badge {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 4px 12px; border-radius: var(--radius-full);
  background: var(--accent-soft); border: 1px solid var(--accent);
  font-size: 12px; font-weight: 600; color: var(--accent);
  margin-bottom: 12px; letter-spacing: 0.05em; text-transform: uppercase;
}
.seo-intro {
  font-size: 17px; line-height: 1.7; color: var(--text-soft);
  max-width: 780px; margin-bottom: 0;
}
.seo-intro p { margin: 0 0 16px; }
.seo-intro p:last-child { margin-bottom: 0; }

/* Benefits grid */
.benefits-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.benefit-card {
  background: var(--bg-soft); border-radius: var(--radius-xl);
  padding: 16px; border: 1px solid var(--border-soft);
  display: flex; gap: 12px; align-items: flex-start;
}
.benefit-icon { font-size: 22px; flex-shrink: 0; line-height: 1; margin-top: 2px; }
.benefit-title { font-size: 15px; font-weight: 600; margin-bottom: 4px; }
.benefit-text { font-size: 14px; color: var(--text-soft); line-height: 1.5; }

/* Sample stories */
.sample-card {
  border-radius: var(--radius-xl); border: 1px solid var(--border-soft);
  overflow: hidden; margin-bottom: 20px;
  box-shadow: var(--shadow-soft);
}
.sample-header {
  background: var(--bg-softer); padding: 10px 16px;
  display: flex; justify-content: space-between; align-items: center;
  font-size: 13px; color: var(--text-muted);
  border-bottom: 1px solid var(--border-soft);
}
.sample-header strong { color: var(--text-main); font-size: 14px; }
.sample-chips { display: flex; gap: 6px; }
.chip-sm {
  font-size: 10px; padding: 2px 8px; border-radius: 999px;
  background: var(--bg-soft); border: 1px solid var(--border-soft);
  color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.1em;
}
.parallel-columns {
  display: grid; grid-template-columns: 1fr 1fr;
}
.parallel-col {
  padding: 16px; font-size: 15px; line-height: 1.7; color: var(--text-soft);
}
.parallel-col:first-child {
  border-right: 1px solid var(--border-soft);
  color: var(--text-main);
}
.parallel-col-label {
  font-size: 10px; text-transform: uppercase; letter-spacing: 0.12em;
  color: var(--text-muted); margin-bottom: 8px; font-weight: 600;
}
.vocab-strip {
  padding: 10px 16px; background: var(--bg-soft);
  border-top: 1px solid var(--border-soft);
  display: flex; flex-wrap: wrap; gap: 8px; align-items: center;
}
.vocab-strip-label { font-size: 11px; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.1em; margin-right: 4px; }
.vocab-pill {
  font-size: 12px; padding: 3px 10px; border-radius: 999px;
  background: var(--accent-soft); border: 1px solid rgba(37, 99, 235, 0.2);
  color: var(--accent); font-weight: 500;
}
[data-theme="dark"] .vocab-pill { border-color: rgba(96, 165, 250, 0.25); }

/* BiReader features */
.bireader-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 14px; }
.bireader-card {
  background: var(--bg-soft); border-radius: var(--radius-xl);
  padding: 14px; border: 1px solid var(--border-soft);
}
.bireader-icon { font-size: 20px; margin-bottom: 8px; }
.bireader-title { font-size: 14px; font-weight: 600; margin-bottom: 4px; }
.bireader-text { font-size: 13px; color: var(--text-soft); line-height: 1.5; }

/* Related links */
.related-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(210px, 1fr)); gap: 10px; }
.related-link {
  display: flex; align-items: center; gap: 8px;
  padding: 10px 14px; border-radius: 12px;
  background: var(--bg-soft); border: 1px solid var(--border-soft);
  text-decoration: none; color: var(--text-soft); font-size: 14px;
  transition: all 0.15s ease;
}
.related-link:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); transform: translateY(-1px); }
.related-link-arrow { margin-left: auto; opacity: 0.5; font-size: 12px; }

/* CEFR table */
.cefr-table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 14px; }
.cefr-table th, .cefr-table td { padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--border-soft); }
.cefr-table th { background: var(--bg-soft); font-weight: 600; color: var(--text-main); font-size: 13px; text-transform: uppercase; letter-spacing: .04em; }
.cefr-table td { color: var(--text-soft); }
.cefr-table tbody tr:last-child td { border-bottom: none; }
.cefr-table tbody tr:hover td { background: var(--bg-soft); }

/* Topic chips */
.topic-chips { display: flex; flex-wrap: wrap; gap: 8px; margin: 18px 0 4px; }
.topic-chip {
  background: var(--bg-soft); border: 1px solid var(--border-soft); border-radius: 20px;
  padding: 4px 12px; font-size: 13px; color: var(--text-soft);
}

/* Responsive */
@media (max-width: 900px) {
  header { flex-direction: column; align-items: flex-start; }
  nav { width: 100%; justify-content: space-between; }
  .features-grid, .faq-grid, .bireader-grid { grid-template-columns: minmax(0, 1fr); }
  .benefits-grid { grid-template-columns: minmax(0, 1fr); }
  .parallel-columns { grid-template-columns: 1fr; }
  .parallel-col:first-child { border-right: none; border-bottom: 1px solid var(--border-soft); }
}
@media (max-width: 640px) {
  .page { padding: 18px 14px 40px; }
  nav { flex-wrap: wrap; gap: 10px; }
  .seo-hero h1 { font-size: 26px; }
  .bireader-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 400px) {
  .bireader-grid { grid-template-columns: minmax(0, 1fr); }
}