:root {
  --bg-page: #f4f6f9;
  --bg-card: #ffffff;
  --bg-navy: #0f2537;
  --bg-navy-accent: #183650;
  --bg-callout: #f8fafc;
  --text-main: #1a202c;
  --text-muted: #4a5568;
  --accent-blue: #1d5b8c;
  --accent-blue-hover: #144369;
  --accent-gold: #c98a27;
  --border-light: #dce3ec;
  --shadow-card: 0 10px 30px rgba(15, 37, 55, 0.08);
  --radius-lg: 12px;
  --radius-md: 8px;
}

*, *::before, *::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text-main);
  background-color: var(--bg-page);
  line-height: 1.7;
  font-size: 18px;
  -webkit-font-smoothing: antialiased;
}

/* Top bar */
.site-header {
  background: var(--bg-navy);
  color: #ffffff;
  border-bottom: 4px solid var(--accent-gold);
  padding: 1rem 1.5rem;
}

.header-inner {
  max-width: 1040px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand-wrap {
  display: flex;
  flex-direction: column;
}

.brand-domain {
  font-size: 1.25rem;
  font-weight: 800;
  letter-spacing: 0.03em;
  color: #ffffff;
  text-decoration: none;
}

.brand-sub {
  font-size: 0.875rem;
  color: #cbd5e1;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.header-badge {
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.25);
  color: #f8fafc;
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
}

.btn-header {
  background: var(--accent-gold);
  color: #0f2537;
  font-weight: 700;
  font-size: 0.92rem;
  padding: 0.45rem 1rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: background 0.15s ease, transform 0.15s ease;
}

.btn-header:hover {
  background: #df9b30;
}

/* Main container */
.container {
  max-width: 960px;
  margin: 2.5rem auto 4rem;
  padding: 0 1.25rem;
}

/* Hero / Letter Card */
.letter-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  overflow: hidden;
  margin-bottom: 3rem;
}

.letter-banner {
  background: linear-gradient(135deg, var(--bg-navy) 0%, var(--bg-navy-accent) 100%);
  color: #ffffff;
  padding: 2.5rem 2.5rem 2.25rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.eyebrow-pill {
  display: inline-block;
  background: rgba(201, 138, 39, 0.22);
  border: 1px solid #e6a945;
  color: #ffd485;
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 0.28rem 0.75rem;
  border-radius: 999px;
  margin-bottom: 0.9rem;
}

.letter-banner h1 {
  margin: 0 0 0.75rem;
  font-size: clamp(1.85rem, 4vw, 2.65rem);
  font-weight: 800;
  letter-spacing: 0.02em;
  line-height: 1.2;
  color: #ffffff;
}

.letter-lead {
  margin: 0;
  font-size: clamp(1.1rem, 2.2vw, 1.32rem);
  color: #e2e8f0;
  font-weight: 500;
  line-height: 1.5;
}

.letter-body {
  padding: 2.5rem;
}

.letter-prose p {
  margin: 0 0 1.4rem;
  font-size: 1.15rem;
  line-height: 1.8;
  color: var(--text-main);
}

.letter-prose p.price-highlight {
  background: #fffbeb;
  border-left: 5px solid var(--accent-gold);
  padding: 1.15rem 1.35rem;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-weight: 600;
  color: #1e293b;
}

/* Patent Facts & Contact Grid */
.patent-details-box {
  margin-top: 2rem;
  background: var(--bg-callout);
  border: 2px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 1.75rem 2rem;
}

.patent-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.25rem;
  margin-bottom: 1.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border-light);
}

.fact-item {
  display: flex;
  flex-direction: column;
}

.fact-label {
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.fact-value {
  font-size: 1.12rem;
  font-weight: 700;
  color: var(--bg-navy);
}

.fact-value a {
  color: var(--accent-blue);
  text-decoration: underline;
}

.fact-value a:hover {
  color: var(--accent-blue-hover);
}

.patent-Credentials-raw {
  margin: 0 0 1.5rem;
  padding: 1rem 1.25rem;
  background: #ffffff;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  font-size: 1.02rem;
  line-height: 1.75;
}

.patent-Credentials-raw p {
  margin: 0.2rem 0;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--accent-blue);
  color: #ffffff;
  font-weight: 700;
  font-size: 1.05rem;
  padding: 0.85rem 1.5rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: background 0.15s ease;
}

.btn-primary:hover {
  background: var(--accent-blue-hover);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: #ffffff;
  color: var(--bg-navy);
  border: 2px solid var(--bg-navy);
  font-weight: 700;
  font-size: 0.98rem;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: background 0.15s ease, color 0.15s ease;
}

.btn-secondary:hover {
  background: var(--bg-navy);
  color: #ffffff;
}

/* Video Section */
.videos-section {
  margin-top: 1rem;
}

.section-header {
  text-align: center;
  margin-bottom: 2rem;
}

.section-header h2 {
  margin: 0 0 0.5rem;
  font-size: clamp(1.55rem, 3vw, 2.1rem);
  color: var(--bg-navy);
  font-weight: 800;
}

.section-header p {
  margin: 0;
  color: var(--text-muted);
  font-size: 1.05rem;
}

.video-list {
  display: flex;
  flex-direction: column;
  gap: 2.25rem;
}

.video-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}

.video-card-header {
  padding: 1.35rem 1.75rem;
  background: #ffffff;
  border-bottom: 1px solid var(--border-light);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.video-step-title {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.video-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.1rem;
  height: 2.1rem;
  border-radius: 50%;
  background: var(--bg-navy);
  color: #ffffff;
  font-weight: 800;
  font-size: 0.95rem;
  flex-shrink: 0;
}

.video-card-header h3 {
  margin: 0;
  font-size: 1.3rem;
  color: var(--bg-navy);
  font-weight: 700;
}

.video-duration {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-muted);
  background: var(--bg-page);
  padding: 0.3rem 0.7rem;
  border-radius: 999px;
}

/* Responsive 16:9 Vimeo wrapper */
.video-embed-wrap {
  position: relative;
  width: 100%;
  padding-bottom: 56.25%;
  height: 0;
  background: #0b1520;
}

.video-embed-wrap iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.video-card-footer {
  padding: 1rem 1.75rem;
  background: var(--bg-callout);
  border-top: 1px solid var(--border-light);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  font-size: 0.95rem;
}

.video-caption {
  color: var(--text-muted);
  margin: 0;
}

.vimeo-direct-link {
  font-weight: 700;
  color: var(--accent-blue);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

.vimeo-direct-link:hover {
  text-decoration: underline;
  color: var(--accent-blue-hover);
}

/* Footer */
.site-footer {
  background: var(--bg-navy);
  color: #cbd5e1;
  padding: 2.5rem 1.5rem;
  text-align: center;
  border-top: 4px solid var(--accent-gold);
}

.footer-inner {
  max-width: 840px;
  margin: 0 auto;
}

.footer-inner p {
  margin: 0.4rem 0;
  font-size: 0.98rem;
}

.footer-inner a {
  color: #ffd485;
  text-decoration: underline;
}

@media (max-width: 820px) {
  .patent-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 680px) {
  .letter-banner,
  .letter-body {
    padding: 1.5rem;
  }

  .patent-details-box {
    padding: 1.25rem;
  }

  .video-card-header,
  .video-card-footer {
    padding: 1rem 1.25rem;
  }

  .cta-row {
    flex-direction: column;
    align-items: stretch;
  }

  .btn-primary,
  .btn-secondary {
    justify-content: center;
    text-align: center;
  }
}