/* ============================================================
   HCI Explained — Stylesheet
   Aesthetic: cinematic dark, intelligent editorial
   Fonts: Cormorant Garamond (headings) + DM Sans (body)
   Colors: deep charcoal, muted blue accent, cool-grey type
============================================================ */

/* ============================================================
   CSS CUSTOM PROPERTIES
============================================================ */
:root {
  /* Dark cinematic colour palette */
  --bg:           #0B0F14;               /* deep charcoal — main bg */
  --bg-alt:       #121821;               /* secondary surface */
  --bg-card:      #171F2B;               /* elevated card */
  --bg-elevated:  #1C2535;               /* higher elevation */
  --ink:          #F3F5F7;               /* primary text — near white */
  --ink-muted:    #A7B0BA;               /* secondary text — cool grey */
  --ink-light:    #6B7885;               /* tertiary text */
  --accent:       #5FA8FF;               /* muted electric blue */
  --accent-dim:   rgba(95,168,255,0.08); /* very subtle accent tint */
  --accent-soft:  rgba(95,168,255,0.15); /* soft accent fill */
  --accent-glow:  rgba(95,168,255,0.10); /* hover glow */
  --border:       rgba(255,255,255,0.08);  /* subtle border */
  --border-dark:  rgba(255,255,255,0.16);  /* stronger border */

  /* Typography */
  --font-heading: 'Cormorant Garamond', Georgia, serif;
  --font-body:    'DM Sans', 'Helvetica Neue', sans-serif;

  /* Spacing scale */
  --space-xs:  0.25rem;
  --space-sm:  0.5rem;
  --space-md:  1rem;
  --space-lg:  1.5rem;
  --space-xl:  2.5rem;
  --space-2xl: 4rem;
  --space-3xl: 6rem;

  /* Layout */
  --max-width:    1100px;
  --radius-sm:    4px;
  --radius-md:    8px;
  --radius-lg:    16px;

  /* Shadows — dark-mode depth */
  --shadow-sm:  0 1px 3px rgba(0,0,0,0.35), 0 1px 2px rgba(0,0,0,0.25);
  --shadow-md:  0 4px 20px rgba(0,0,0,0.45), 0 2px 8px rgba(0,0,0,0.25);
  --shadow-lg:  0 8px 40px rgba(0,0,0,0.55), 0 4px 16px rgba(0,0,0,0.35);

  /* Transitions */
  --transition: 200ms ease;
}

/* ============================================================
   RESET & BASE
============================================================ */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  background-color: var(--bg);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 300;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Subtle dot grid texture — nearly invisible depth layer */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image: radial-gradient(rgba(255,255,255,0.018) 1px, transparent 1px);
  background-size: 36px 36px;
  pointer-events: none;
  z-index: -1;
}

img, video, iframe {
  max-width: 100%;
  display: block;
}

a {
  color: inherit;
  text-decoration: none;
}

ul { list-style: none; }

/* ============================================================
   TYPOGRAPHY
============================================================ */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: 400;
  line-height: 1.15;
  letter-spacing: -0.01em;
}

h1 { font-size: clamp(3.5rem, 8vw, 6.5rem); }
h2 { font-size: clamp(2rem, 4vw, 3rem); }
h3 { font-size: clamp(1.2rem, 2vw, 1.5rem); }

p + p { margin-top: var(--space-md); }

/* ============================================================
   LAYOUT UTILITIES
============================================================ */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.section {
  padding: var(--space-3xl) 0;
}

/* ============================================================
   NAVIGATION
============================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(11, 15, 20, 0.88);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: var(--space-xl);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 500;
  letter-spacing: 0.01em;
  color: var(--ink);
  transition: opacity var(--transition);
  white-space: nowrap;
  flex-shrink: 0;
}

.nav-logo:hover { opacity: 0.7; }

.logo-mark {
  color: var(--accent);
  font-size: 1.3em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 400;
  color: var(--ink-muted);
  letter-spacing: 0.03em;
  transition: color var(--transition);
  white-space: nowrap;
}

.nav-links a:hover { color: var(--ink); }

.nav-links .nav-cta {
  color: var(--accent);
  border: 1px solid rgba(95,168,255,0.35);
  padding: 0.35rem 0.9rem;
  border-radius: var(--radius-sm);
  transition: background var(--transition), color var(--transition), border-color var(--transition);
}

.nav-links .nav-cta:hover {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--ink);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 1.5px;
  background: var(--ink-muted);
  transition: transform var(--transition), opacity var(--transition);
}

/* ============================================================
   HERO
============================================================ */
.hero {
  position: relative;
  overflow: hidden;
  padding: var(--space-3xl) 0 var(--space-2xl);
  min-height: 82vh;
  display: flex;
  align-items: center;
  border-bottom: 1px solid var(--border);
}

/* Ambient radial lighting — atmospheric, nearly invisible */
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 90% 70% at 10% 50%, rgba(95,168,255,0.05) 0%, transparent 55%),
    radial-gradient(ellipse 60% 50% at 85% 15%, rgba(95,168,255,0.04) 0%, transparent 50%),
    radial-gradient(ellipse 40% 60% at 60% 80%, rgba(95,168,255,0.025) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
}

.hero-bg {
  position: absolute;
  inset: 0;
  opacity: 0.18;
  pointer-events: none;
}

.hero-svg {
  width: 100%;
  height: 100%;
}

.node {
  fill: var(--accent);
}

.edge {
  stroke: var(--accent);
  stroke-width: 0.8;
  opacity: 0.35;
}

.hero-content {
  position: relative;
  z-index: 1;
}

.hero-eyebrow {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-xl);
}

.eyebrow-line {
  display: block;
  height: 1px;
  width: 40px;
  background: var(--border-dark);
}

.eyebrow-text {
  font-size: 0.8rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-light);
  font-weight: 400;
}

.hero-title {
  margin-bottom: var(--space-xl);
  color: var(--ink);
}

.hero-title em {
  font-style: italic;
  color: var(--accent);
}

.hero-subtitle {
  font-family: var(--font-heading);
  font-size: clamp(1.1rem, 2vw, 1.45rem);
  font-weight: 300;
  color: var(--ink-muted);
  margin-bottom: var(--space-md);
  max-width: 600px;
  line-height: 1.45;
}

.hero-body {
  font-size: 0.975rem;
  color: var(--ink-light);
  max-width: 500px;
  margin-bottom: var(--space-xl);
}

.br-desktop { display: inline; }

.hero-actions {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
  margin-bottom: var(--space-xl);
}

.hero-topics {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.topic-chip {
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  color: var(--ink-light);
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--border);
  padding: 0.25rem 0.65rem;
  border-radius: 100px;
  transition: color var(--transition), border-color var(--transition);
}

.topic-chip:hover {
  color: var(--ink-muted);
  border-color: var(--border-dark);
}

/* ============================================================
   BUTTONS
============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 400;
  letter-spacing: 0.03em;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition);
  cursor: pointer;
  border: none;
  text-decoration: none;
}

.btn-primary {
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid rgba(95,168,255,0.3);
}

.btn-primary:hover {
  background: rgba(95,168,255,0.22);
  border-color: var(--accent);
  box-shadow: 0 0 20px rgba(95,168,255,0.08);
  transform: translateY(-1px);
}

.btn-secondary {
  background: rgba(255,255,255,0.04);
  color: var(--ink-muted);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: rgba(255,255,255,0.08);
  color: var(--ink);
  border-color: var(--border-dark);
  transform: translateY(-1px);
}

/* ============================================================
   SECTION HEADERS
============================================================ */
.section-label {
  display: inline-block;
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 500;
  margin-bottom: var(--space-md);
}

.section-title {
  margin-bottom: var(--space-md);
  color: var(--ink);
}

.section-desc {
  font-size: 1rem;
  color: var(--ink-muted);
  max-width: 520px;
}

.section-header {
  margin-bottom: var(--space-2xl);
}

/* ============================================================
   ABOUT SECTION
============================================================ */
.about {
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.about-grid {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: var(--space-2xl);
  align-items: start;
}

.about-label {
  padding-top: 0.5rem;
}

.about-body {
  font-size: 1.05rem;
  color: var(--ink-muted);
  max-width: 640px;
  margin-bottom: var(--space-2xl);
}

.about-pillars {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-lg);
}

.pillar {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 0.9rem;
  color: var(--ink-muted);
}

.pillar-icon {
  color: var(--accent);
  font-size: 1.1rem;
}

/* ============================================================
   PODCAST SECTION
============================================================ */
.podcast-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

.episode-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition), border-color var(--transition);
}

.episode-card:hover {
  box-shadow: var(--shadow-md), 0 0 30px rgba(95,168,255,0.04);
  border-color: var(--border-dark);
  transform: translateY(-2px);
}

.episode-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.episode-number {
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 500;
  flex-shrink: 0;
}

.episode-title {
  font-family: var(--font-heading);
  font-size: clamp(1.15rem, 2vw, 1.4rem);
  font-weight: 500;
  color: var(--ink);
  margin-bottom: var(--space-sm);
  line-height: 1.2;
}

.episode-desc {
  font-size: 0.9rem;
  color: var(--ink-muted);
  line-height: 1.6;
  margin-bottom: var(--space-md);
}

.episode-meta {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
  flex-wrap: wrap;
}

.episode-duration {
  font-size: 0.8rem;
  color: var(--ink-light);
  display: flex;
  align-items: center;
  gap: 4px;
}

.episode-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.tag {
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  color: var(--accent);
  background: var(--accent-dim);
  padding: 0.2rem 0.55rem;
  border-radius: 100px;
  font-weight: 500;
  border: 1px solid rgba(95,168,255,0.12);
}

/* Podcast loading state */
.podcast-loading {
  text-align: center;
  color: var(--ink-light);
  font-size: 0.9rem;
  padding: var(--space-2xl) 0;
}

/* "See all on Spotify" CTA below episode grid */
.podcast-see-more {
  display: flex;
  justify-content: center;
  margin-top: var(--space-xl);
}

/* HTML5 audio player */
.episode-audio {
  width: 100%;
  height: 40px;
  margin-top: var(--space-md);
  border-radius: var(--radius-sm);
  accent-color: var(--accent);
}

/* ============================================================
   VIDEO SECTION
============================================================ */
.videos {
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: var(--space-lg);
}

.video-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition), border-color var(--transition);
}

.video-card:hover {
  box-shadow: var(--shadow-md), 0 0 30px rgba(95,168,255,0.04);
  border-color: var(--border-dark);
  transform: translateY(-2px);
}

/* Responsive 16:9 video embed wrapper */
.video-embed-wrapper {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  background: #0A0D11;
}

.video-embed-wrapper iframe {
  position: absolute;
  top: 0; left: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.video-card-body {
  padding: var(--space-lg);
}

.video-card-meta {
  margin-bottom: var(--space-sm);
}

.video-title {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  color: var(--ink);
  margin-bottom: var(--space-sm);
  line-height: 1.25;
}

.video-desc {
  font-size: 0.875rem;
  color: var(--ink-muted);
  line-height: 1.6;
  margin-bottom: var(--space-md);
}

/* ============================================================
   EPISODE LIBRARY
============================================================ */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-bottom: var(--space-2xl);
}

.filter-btn {
  font-family: var(--font-body);
  font-size: 0.82rem;
  font-weight: 400;
  letter-spacing: 0.04em;
  color: var(--ink-muted);
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--border);
  padding: 0.4rem 0.9rem;
  border-radius: 100px;
  cursor: pointer;
  transition: all var(--transition);
}

.filter-btn:hover {
  border-color: var(--border-dark);
  color: var(--ink);
  background: rgba(255,255,255,0.07);
}

.filter-btn.active {
  background: var(--accent-soft);
  border-color: rgba(95,168,255,0.4);
  color: var(--accent);
}

.library-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-md);
}

.library-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition), border-color var(--transition);
}

.library-card:hover {
  box-shadow: var(--shadow-md), 0 0 24px rgba(95,168,255,0.04);
  border-color: var(--border-dark);
  transform: translateY(-1px);
}

.library-card-type {
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-light);
  margin-bottom: var(--space-sm);
}

.library-card-type.podcast { color: var(--accent); }
.library-card-type.video   { color: #7EBFE0; }  /* muted steel teal for video */

.library-card-title {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  color: var(--ink);
  margin-bottom: var(--space-sm);
  line-height: 1.25;
}

.library-card-desc {
  font-size: 0.85rem;
  color: var(--ink-muted);
  line-height: 1.55;
  margin-bottom: var(--space-md);
}

.library-empty {
  grid-column: 1 / -1;
  text-align: center;
  color: var(--ink-light);
  font-size: 0.9rem;
  padding: var(--space-2xl) 0;
}

/* ============================================================
   SUBSCRIBE SECTION
============================================================ */
.subscribe {
  background: #07090D;
  border-top: 1px solid var(--border);
}

.subscribe .section-label {
  color: var(--accent);
}

.subscribe .section-title {
  color: var(--ink);
}

.subscribe .section-desc {
  color: var(--ink-muted);
}

.subscribe-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: var(--space-md);
}

.subscribe-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: var(--space-sm);
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  color: var(--ink);
  text-decoration: none;
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
}

.subscribe-card:hover {
  background: rgba(255,255,255,0.08);
  border-color: var(--border-dark);
  transform: translateY(-2px);
}

.subscribe-icon {
  color: var(--accent);
  opacity: 0.85;
}

.subscribe-platform {
  font-weight: 500;
  font-size: 0.95rem;
  color: var(--ink);
}

.subscribe-detail {
  font-size: 0.8rem;
  color: var(--ink-light);
}

/* ============================================================
   NEWSLETTER FORM
============================================================ */
.newsletter-wrap {
  margin-top: var(--space-2xl);
  padding-top: var(--space-2xl);
  border-top: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-md);
  text-align: center;
}

.newsletter-lead {
  font-size: 0.95rem;
  color: var(--ink-muted);
}

.newsletter-form {
  display: flex;
  gap: var(--space-sm);
  width: 100%;
  max-width: 440px;
}

.newsletter-input {
  flex: 1;
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 300;
  padding: 0.75rem 1rem;
  outline: none;
  transition: border-color var(--transition), background var(--transition);
  -webkit-appearance: none;
}

.newsletter-input::placeholder {
  color: var(--ink-light);
}

.newsletter-input:focus {
  border-color: rgba(95,168,255,0.45);
  background: rgba(255,255,255,0.07);
}

.newsletter-btn {
  white-space: nowrap;
  flex-shrink: 0;
}

.newsletter-note {
  font-size: 0.82rem;
  color: var(--ink-light);
  letter-spacing: 0.02em;
}

@media (max-width: 540px) {
  .newsletter-form {
    flex-direction: column;
  }

  .newsletter-btn {
    justify-content: center;
  }
}

/* ============================================================
   FOOTER
============================================================ */
.site-footer {
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
  padding: var(--space-2xl) 0;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
  text-align: center;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-heading);
  font-size: 1.1rem;
  color: var(--ink);
}

.footer-tagline {
  font-size: 0.9rem;
  color: var(--ink-muted);
}

.footer-copy {
  font-size: 0.78rem;
  color: var(--ink-light);
  margin-top: var(--space-sm);
}

/* ============================================================
   RESPONSIVE — TABLET
============================================================ */
@media (max-width: 860px) {
  .container {
    padding: 0 var(--space-lg);
  }

  .about-grid {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }

  .about-label {
    display: none;
  }

  .nav-links {
    display: none;
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: rgba(11, 15, 20, 0.97);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--space-lg);
    gap: var(--space-lg);
    box-shadow: var(--shadow-md);
  }

  .nav-links.open {
    display: flex;
  }

  .nav-toggle {
    display: flex;
  }

  .hero {
    min-height: auto;
    padding: var(--space-2xl) 0;
  }

  .br-desktop {
    display: none;
  }
}

/* ============================================================
   RESPONSIVE — MOBILE
============================================================ */
@media (max-width: 540px) {
  :root {
    --space-3xl: 3.5rem;
    --space-2xl: 2.5rem;
  }

  .hero-actions {
    flex-direction: column;
  }

  .hero-actions .btn {
    justify-content: center;
  }

  .video-grid,
  .library-grid {
    grid-template-columns: 1fr;
  }

  .subscribe-grid {
    grid-template-columns: 1fr 1fr;
  }

  .filter-bar {
    gap: var(--space-xs);
  }
}

/* ============================================================
   ACCESSIBILITY — FOCUS STYLES
============================================================ */
a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 2px;
}

/* ============================================================
   SCROLL FADE-IN ANIMATION (JS adds .visible class)
============================================================ */
.fade-in {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}