/* ── Reset & Base ── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --bg: #ffffff;
  --card-bg: #f7f8fa;
  --card-border: #e5e7eb;
  --text-primary: #111827;
  --text-muted: #6b7280;
  --cta-bg: #1d4ed8;
  --cta-text: #ffffff;
  --radius-card: 10px;
  --radius-btn: 6px;
  --max-w: 1140px;
}

html { scroll-behavior: smooth; }

body {
  font-family: 'IBM Plex Sans', system-ui, sans-serif;
  color: var(--text-primary);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 { font-family: 'Source Serif 4', Georgia, serif; font-weight: 600; line-height: 1.2; }
h1 { font-size: 2.75rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.25rem; }
h4 { font-family: 'IBM Plex Sans', sans-serif; font-size: 0.9375rem; font-weight: 600; }

a { color: var(--text-primary); text-decoration: none; }
img { max-width: 100%; display: block; }

.container { max-width: var(--max-w); margin: 0 auto; padding: 0 24px; }

/* ── Utilities ── */
.text-muted { color: var(--text-muted); font-size: 0.9375rem; line-height: 1.55; }
.text-center { text-align: center; }
.small { font-size: 0.8125rem; }
.mt-2 { margin-top: 8px; }
.mt-4 { margin-top: 16px; }
.mt-6 { margin-top: 32px; }
.w-full { width: 100%; }

/* ── Eyebrow ── */
.eyebrow {
  font-family: 'IBM Plex Mono', monospace;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 12px;
}

/* ── Buttons ── */
.btn {
  display: inline-block;
  font-family: 'IBM Plex Sans', sans-serif;
  font-size: 0.9375rem;
  font-weight: 600;
  padding: 12px 28px;
  border-radius: var(--radius-btn);
  border: 1.5px solid transparent;
  cursor: pointer;
  transition: opacity 0.15s;
  text-align: center;
}
.btn:hover { opacity: 0.85; }

.btn-primary {
  background: var(--cta-bg);
  color: var(--cta-text);
  border-color: var(--cta-bg);
}

.btn-lg {
  padding: 14px 32px;
  font-size: 1rem;
}

/* ── Site Header / Nav ── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg);
  border-bottom: 1px solid var(--card-border);
}

.site-header .nav {
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand { display: flex; align-items: center; gap: 10px; }
.nav-brand img { height: 36px; width: auto; border-radius: 4px; }
.nav-brand-text { display: flex; flex-direction: column; line-height: 1.3; }
.nav-brand-name { font-size: 0.9375rem; font-weight: 600; }
.nav-brand-sub { font-size: 0.75rem; color: var(--text-muted); }

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  list-style: none;
}
.nav-links a { font-size: 0.9375rem; color: var(--text-primary); }
.nav-links a:hover { color: var(--text-muted); }
.nav-links .btn { padding: 8px 20px; font-size: 0.875rem; }
.nav-links .btn-primary { color: #ffffff; }

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-primary);
  padding: 4px;
}

/* ── Sections ── */
.section { padding: 96px 0; }

.section-alt { background: var(--card-bg); }

.section-sub {
  color: var(--text-muted);
  font-size: 1.0625rem;
  margin-bottom: 32px;
  max-width: 640px;
}
.text-center .section-sub { margin-left: auto; margin-right: auto; }

/* ── About ── */
.about-text { max-width: 640px; }
.about-text p {
  color: var(--text-muted);
  font-size: 1.0625rem;
  margin-bottom: 16px;
  line-height: 1.6;
}
.about-text p:last-child { margin-bottom: 0; }

/* ── Hero ── */
.hero { padding: 100px 0 80px; }
.hero h1 { max-width: 680px; margin-bottom: 20px; }
.hero-sub { max-width: 560px; color: var(--text-muted); font-size: 1.125rem; margin-bottom: 32px; }

.hero-sm { padding: 80px 0 48px; }
.hero-sm h1 { max-width: 580px; margin-bottom: 20px; }

/* ── Cards ── */
.card-grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.card-grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }

.card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-card);
  padding: 28px;
}
.section-alt .card { background: var(--bg); }

.card h3 { margin-bottom: 10px; }
.card h4 { margin-bottom: 10px; }
.card p { color: var(--text-muted); font-size: 0.9375rem; line-height: 1.55; }

.link-arrow {
  display: inline-block;
  margin-top: 16px;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-primary);
}
.link-arrow:hover { color: var(--text-muted); }

/* ── Bullet list ── */
.bullet-list {
  list-style: none;
  margin: 16px 0 0;
  padding: 0;
}
.bullet-list li {
  position: relative;
  padding-left: 18px;
  font-size: 0.9375rem;
  color: var(--text-muted);
  margin-bottom: 8px;
  line-height: 1.5;
}
.bullet-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 8px;
  width: 6px;
  height: 6px;
  background: var(--card-border);
  border-radius: 50%;
}

/* ── CTA Banner ── */
.cta-banner {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-card);
  padding: 48px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 40px;
}
.cta-banner h2 { margin-bottom: 12px; }
.cta-banner p { color: var(--text-muted); max-width: 520px; font-size: 1rem; }

/* ── Footer ── */
.site-footer {
  background: var(--card-bg);
  border-top: 1px solid var(--card-border);
  padding: 64px 0 48px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1.25fr;
  gap: 48px;
}

.footer-col h4 {
  font-family: 'IBM Plex Sans', sans-serif;
  font-size: 0.8125rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 16px;
  color: var(--text-primary);
}

.footer-links {
  list-style: none;
  padding: 0;
}
.footer-links li { margin-bottom: 8px; }
.footer-links a { font-size: 0.9375rem; color: var(--text-muted); }
.footer-links a:hover { color: var(--text-primary); }

.footer-col p { font-size: 0.875rem; color: var(--text-muted); line-height: 1.55; }

/* ── Book page ── */
.book-layout {
  display: grid;
  grid-template-columns: 2fr 3fr;
  gap: 48px;
  align-items: start;
}

.book-left h1 { font-size: 2.25rem; margin-bottom: 16px; }
.book-left > p { color: var(--text-muted); font-size: 1rem; margin-bottom: 0; }

/* ── Form ── */
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-bottom: 16px; }

.form-group { display: flex; flex-direction: column; margin-bottom: 16px; }
.form-row .form-group { margin-bottom: 0; }

.form-group label {
  font-size: 0.8125rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-primary);
}

.form-group input,
.form-group textarea {
  font-family: 'IBM Plex Sans', sans-serif;
  font-size: 0.9375rem;
  padding: 10px 14px;
  border: 1px solid var(--card-border);
  border-radius: var(--radius-btn);
  background: var(--bg);
  color: var(--text-primary);
  transition: border-color 0.15s;
}
.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--cta-bg);
}
.form-group textarea { resize: vertical; }

/* Radio options */
.radio-group {
  display: flex;
  gap: 12px;
}

.radio-option {
  flex: 1;
  position: relative;
  border: 1.5px solid var(--card-border);
  border-radius: var(--radius-btn);
  padding: 14px 16px;
  cursor: pointer;
  background: var(--bg);
  transition: border-color 0.15s;
  display: flex;
  align-items: flex-start;
  gap: 10px;
}
.radio-option:hover { border-color: #9ca3af; }
.radio-option:has(input:checked) { border-color: var(--cta-bg); }

.radio-option input[type="radio"] { margin-top: 3px; }

.radio-content { display: flex; flex-direction: column; }
.radio-title { font-weight: 600; font-size: 0.9375rem; }
.radio-sub { font-size: 0.8125rem; color: var(--text-muted); }

.form-feedback {
  margin-top: 16px;
  padding: 14px;
  border-radius: var(--radius-btn);
  font-size: 0.9375rem;
}
.form-feedback.success {
  background: #ecfdf5;
  color: #065f46;
  border: 1px solid #a7f3d0;
}
.form-feedback.error {
  background: #fef2f2;
  color: #991b1b;
  border: 1px solid #fecaca;
}

/* ── 404 ── */
.page-404 {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}
.page-404 h1 { font-size: 2.75rem; margin-bottom: 12px; }
.page-404 p { color: var(--text-muted); margin-bottom: 24px; font-size: 1.125rem; }
.page-404 a { font-weight: 600; }
.page-404 a:hover { color: var(--text-muted); }

/* ── Mobile ── */
@media (max-width: 768px) {
  h1 { font-size: 2rem; }
  h2 { font-size: 1.5rem; }
  .section { padding: 56px 0; }

  .nav-toggle { display: block; }

  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--card-border);
    flex-direction: column;
    padding: 20px 24px;
    gap: 16px;
  }
  .nav-links.open { display: flex; }

  .card-grid-3,
  .card-grid-2 { grid-template-columns: 1fr; }

  .cta-banner { flex-direction: column; text-align: center; padding: 32px 24px; }

  .footer-grid { grid-template-columns: 1fr; gap: 32px; }

  .book-layout { grid-template-columns: 1fr; }

  .form-row { grid-template-columns: 1fr; }

  .radio-group { flex-direction: column; }

  .hero { padding: 64px 0 56px; }
  .hero-sm { padding: 64px 0 32px; }
}