/* ============================================================
   PHXCUG — Design System & Styles
   Phoenix Cisco Users Group | styles.css
   ============================================================ */

/* ----------------------------------------------------------
   CSS Custom Properties (Design Tokens)
   ---------------------------------------------------------- */
:root {
  /* Brand Colors */
  --color-primary:      #1B4F8C;
  --color-accent:       #2E75B6;
  --color-navy:         #0D1B2A;
  --color-blue-tint:    #D6E4F7;
  --color-blue-light:   #EBF3FF;

  /* Backgrounds */
  --bg-page:            #ffffff;
  --bg-section-alt:     #F5F7FA;
  --bg-card:            #ffffff;
  --bg-card-alt:        #F5F7FA;

  /* Text */
  --text-primary:       #1A1A2E;
  --text-secondary:     #4A5568;
  --text-muted:         #718096;
  --text-on-dark:       #ffffff;
  --text-on-primary:    #ffffff;

  /* Status */
  --color-success:      #1E7B45;
  --color-success-bg:   #E8F5EE;
  --color-error:        #C00000;
  --color-error-bg:     #FEF2F2;
  --color-warning:      #D97706;

  /* Borders */
  --border-color:       #B8CCE4;
  --border-radius-sm:   6px;
  --border-radius-md:   12px;
  --border-radius-lg:   20px;
  --border-radius-xl:   32px;

  /* Shadows */
  --shadow-sm:   0 1px 3px rgba(27,79,140,0.08), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md:   0 4px 16px rgba(27,79,140,0.12), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-lg:   0 10px 40px rgba(27,79,140,0.18), 0 4px 8px rgba(0,0,0,0.06);
  --shadow-card-hover: 0 16px 48px rgba(27,79,140,0.22), 0 6px 12px rgba(0,0,0,0.08);

  /* Typography */
  --font-sans:   'Inter', system-ui, -apple-system, sans-serif;
  --font-mono:   'JetBrains Mono', 'Fira Code', monospace;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-med:  280ms ease;
  --transition-slow: 400ms cubic-bezier(0.16, 1, 0.3, 1);

  /* Layout */
  --container-max:  1200px;
  --section-pad:    5rem;
  --nav-height:     64px;
}

/* Dark mode tokens */
[data-theme="dark"] {
  --bg-page:          #0D1B2A;
  --bg-section-alt:   #132236;
  --bg-card:          #1a2d42;
  --bg-card-alt:      #142030;
  --text-primary:     #E8F1FB;
  --text-secondary:   #A8BDD4;
  --text-muted:       #6B8DAA;
  --border-color:     #2E4A6A;
  --shadow-sm:        0 1px 3px rgba(0,0,0,0.4);
  --shadow-md:        0 4px 16px rgba(0,0,0,0.5);
  --shadow-lg:        0 10px 40px rgba(0,0,0,0.6);
  --shadow-card-hover:0 16px 48px rgba(0,0,0,0.7);
  --color-success-bg: #0d261a;
  --color-error-bg:   #2e0b0b;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.65;
  transition: background-color var(--transition-med), color var(--transition-med);
  overflow-x: hidden;
}

img, svg { display: block; max-width: 100%; }
ul { list-style: none; }
a { color: var(--color-accent); text-decoration: none; transition: color var(--transition-fast); }
a:hover { color: var(--color-primary); }
button { cursor: pointer; font-family: inherit; }
input, select, textarea { font-family: inherit; }

.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Utility */
.hidden { display: none !important; }
.sr-only { position:absolute; width:1px; height:1px; padding:0; overflow:hidden; clip:rect(0,0,0,0); white-space:nowrap; border:0; }

/* ----------------------------------------------------------
   Scroll-fade animations
   ---------------------------------------------------------- */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}
.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ----------------------------------------------------------
   NAVIGATION
   ---------------------------------------------------------- */
.navbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  height: var(--nav-height);
  background: rgba(27, 79, 140, 0.96);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255,255,255,0.08);
  transition: box-shadow var(--transition-med);
}
.navbar.scrolled { box-shadow: 0 4px 24px rgba(0,0,0,0.3); }

.nav-inner {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1.5rem;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  flex-shrink: 0;
}
.logo-badge {
  background: var(--color-accent);
  color: #fff;
  font-weight: 800;
  font-size: 0.85rem;
  letter-spacing: 0.08em;
  padding: 0.2em 0.55em;
  border-radius: var(--border-radius-sm);
}
.logo-text {
  font-weight: 700;
  font-size: 0.95rem;
  color: #fff;
  letter-spacing: 0.04em;
}

.nav-links {
  display: flex;
  gap: 0.25rem;
  align-items: center;
}
.nav-link {
  color: rgba(255,255,255,0.82);
  font-size: 0.9rem;
  font-weight: 500;
  padding: 0.4em 0.85em;
  border-radius: var(--border-radius-sm);
  transition: color var(--transition-fast), background var(--transition-fast);
}
.nav-link:hover, .nav-link.active {
  color: #fff;
  background: rgba(255,255,255,0.12);
}

.nav-actions { display: flex; align-items: center; gap: 0.5rem; }

.dark-toggle {
  width: 40px; height: 40px;
  border: 1.5px solid rgba(255,255,255,0.25);
  border-radius: 50%;
  background: transparent;
  color: #fff;
  font-size: 1rem;
  display: flex; align-items: center; justify-content: center;
  transition: background var(--transition-fast), border-color var(--transition-fast);
}
.dark-toggle:hover { background: rgba(255,255,255,0.12); border-color: rgba(255,255,255,0.5); }

.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px; height: 44px;
  background: transparent;
  border: 1.5px solid rgba(255,255,255,0.25);
  border-radius: var(--border-radius-sm);
  padding: 0 10px;
}
.ham-bar {
  width: 100%; height: 2px;
  background: #fff;
  border-radius: 2px;
  transition: transform var(--transition-med), opacity var(--transition-med);
}
.hamburger.open .ham-bar:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.hamburger.open .ham-bar:nth-child(2) { opacity: 0; }
.hamburger.open .ham-bar:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ----------------------------------------------------------
   HERO
   ---------------------------------------------------------- */
.hero {
  position: relative;
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  background: var(--color-navy);
}

.hero-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(
    135deg,
    rgba(13,27,42,0.82) 0%,
    rgba(27,79,140,0.65) 50%,
    rgba(13,27,42,0.88) 100%
  );
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 2;
  text-align: center;
  padding: 6rem 1.5rem 4rem;
}

.hero-eyebrow {
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: rgba(214,228,247,0.8);
  margin-bottom: 1.2rem;
}

.hero-title {
  font-size: clamp(2.8rem, 7vw, 5.5rem);
  font-weight: 800;
  line-height: 1.08;
  color: #fff;
  margin-bottom: 1.5rem;
  letter-spacing: -0.02em;
}
.hero-title .highlight {
  background: linear-gradient(135deg, #7ab8f5 0%, #d6e4f7 50%, #2E75B6 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-tagline {
  font-size: clamp(1.05rem, 2.5vw, 1.3rem);
  color: rgba(214,228,247,0.88);
  max-width: 560px;
  margin: 0 auto 2.5rem;
  line-height: 1.55;
}

.hero-ctas { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; margin-bottom: 3.5rem; }

.hero-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2rem;
  padding: 1.25rem 2rem;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: var(--border-radius-lg);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  flex-wrap: wrap;
}
.stat { text-align: center; }
.stat-num { display: block; font-size: 1.6rem; font-weight: 800; color: #fff; line-height: 1; }
.stat-label { display: block; font-size: 0.78rem; color: rgba(214,228,247,0.7); margin-top: 0.25rem; letter-spacing: 0.06em; text-transform: uppercase; }
.stat-divider { width: 1px; height: 40px; background: rgba(255,255,255,0.15); }

.hero-scroll-cue {
  position: absolute;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%);
  z-index: 2;
  color: rgba(255,255,255,0.5);
  font-size: 1.3rem;
  animation: bounce 2s infinite;
  text-decoration: none;
}
@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50%       { transform: translateX(-50%) translateY(8px); }
}

/* ----------------------------------------------------------
   BUTTONS
   ---------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75em 1.75em;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--border-radius-md);
  border: 2px solid transparent;
  text-decoration: none;
  transition: all var(--transition-med);
  white-space: nowrap;
  min-height: 44px; /* WCAG touch target */
  min-width: 44px;
}
.btn-primary {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}
.btn-primary:hover {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(46,117,182,0.4);
}
.btn-outline {
  background: transparent;
  color: #fff;
  border-color: rgba(255,255,255,0.5);
}
.btn-outline:hover {
  background: rgba(255,255,255,0.1);
  border-color: #fff;
  color: #fff;
}
.btn-full { width: 100%; }
.btn-spinner {
  width: 18px; height: 18px;
  border: 2.5px solid rgba(255,255,255,0.3);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ----------------------------------------------------------
   SECTIONS — common
   ---------------------------------------------------------- */
.section { padding: var(--section-pad) 0; }
.section-events        { background: var(--bg-page); }
.section-presentations { background: var(--bg-section-alt); }
.section-mailing       { background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-navy) 100%); }
.section-about         { background: var(--bg-page); }

.section-header { text-align: center; margin-bottom: 3rem; }
.section-title {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
  line-height: 1.15;
}
.section-title::after {
  content: '';
  display: block;
  width: 48px; height: 4px;
  background: var(--color-accent);
  border-radius: 2px;
  margin: 0.75rem auto 0;
}
.section-sub { color: var(--text-secondary); font-size: 1.05rem; max-width: 520px; margin: 0 auto; }

/* ----------------------------------------------------------
   EVENTS GRID
   ---------------------------------------------------------- */
.events-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.event-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-med), box-shadow var(--transition-med), border-color var(--transition-med);
  position: relative;
  overflow: hidden;
}
.event-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
}
.event-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-card-hover);
  border-color: var(--color-accent);
}
.event-card.next-event::before {
  background: linear-gradient(90deg, #1E7B45, #38A169);
}

.event-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.73rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 0.3em 0.75em;
  border-radius: 100px;
  margin-bottom: 1rem;
}
.badge-next {
  background: var(--color-success-bg);
  color: var(--color-success);
}
.badge-next .pulse-dot {
  width: 7px; height: 7px;
  background: var(--color-success);
  border-radius: 50%;
  animation: pulse-ring 1.5s ease infinite;
}
.badge-upcoming {
  background: var(--color-blue-tint);
  color: var(--color-primary);
}
@keyframes pulse-ring {
  0%   { box-shadow: 0 0 0 0 rgba(30,123,69,0.5); }
  70%  { box-shadow: 0 0 0 6px rgba(30,123,69,0); }
  100% { box-shadow: 0 0 0 0 rgba(30,123,69,0); }
}

.event-title  { font-size: 1.15rem; font-weight: 700; color: var(--text-primary); margin-bottom: 1rem; line-height: 1.3; }
.event-meta   { display: flex; flex-direction: column; gap: 0.45rem; margin-bottom: 1.25rem; }
.event-meta-item { display: flex; align-items: flex-start; gap: 0.6rem; font-size: 0.88rem; color: var(--text-secondary); }
.event-meta-icon { width: 16px; flex-shrink: 0; font-style: normal; margin-top: 1px; }
.event-speaker { font-size: 0.88rem; color: var(--text-muted); margin-bottom: 1.25rem; }
.event-speaker strong { color: var(--text-secondary); }
.event-tags { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 1.25rem; }
.event-tag { background: var(--color-blue-tint); color: var(--color-primary); font-size: 0.72rem; font-weight: 600; padding: 0.2em 0.6em; border-radius: 100px; }
.event-rsvp { display: inline-flex; align-items: center; gap: 0.4rem; font-size: 0.9rem; font-weight: 600; color: var(--color-accent); }
.event-rsvp:hover { color: var(--color-primary); }
.event-rsvp::after { content: '→'; transition: transform var(--transition-fast); }
.event-rsvp:hover::after { transform: translateX(3px); }

.no-events { text-align: center; padding: 3rem; color: var(--text-secondary); }

/* ----------------------------------------------------------
   PRESENTATIONS FILTER + GRID
   ---------------------------------------------------------- */
.filter-bar {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 2.5rem;
  padding: 1rem 1.25rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
}
.filter-label { font-size: 0.88rem; font-weight: 600; color: var(--text-secondary); white-space: nowrap; }
.filter-select {
  padding: 0.4em 0.75em;
  border: 1.5px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  background: var(--bg-page);
  color: var(--text-primary);
  font-size: 0.88rem;
  min-height: 36px;
}
.tag-filters { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.tag-btn {
  padding: 0.3em 0.85em;
  border: 1.5px solid var(--border-color);
  border-radius: 100px;
  background: var(--bg-page);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 500;
  transition: all var(--transition-fast);
  min-height: 32px;
}
.tag-btn:hover, .tag-btn.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}

.presentations-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem;
}

.pres-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-med), box-shadow var(--transition-med), border-color var(--transition-med);
}
.pres-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-accent);
}
.pres-date { font-size: 0.78rem; font-weight: 600; letter-spacing: 0.06em; color: var(--color-accent); text-transform: uppercase; margin-bottom: 0.5rem; }
.pres-topic { font-size: 1rem; font-weight: 700; color: var(--text-primary); line-height: 1.35; margin-bottom: 0.5rem; }
.pres-speaker { font-size: 0.85rem; color: var(--text-muted); margin-bottom: 1rem; }
.pres-tags { display: flex; flex-wrap: wrap; gap: 0.35rem; margin-bottom: 1rem; }
.pres-tag { background: var(--bg-section-alt); color: var(--text-secondary); font-size: 0.7rem; font-weight: 500; padding: 0.2em 0.55em; border-radius: 100px; border: 1px solid var(--border-color); }
.pres-links { display: flex; gap: 1rem; }
.pres-link {
  display: inline-flex; align-items: center; gap: 0.35rem;
  font-size: 0.82rem; font-weight: 600; color: var(--color-accent);
  padding: 0.35em 0.75em; border-radius: var(--border-radius-sm);
  border: 1.5px solid var(--color-accent); transition: all var(--transition-fast);
}
.pres-link:hover { background: var(--color-accent); color: #fff; }
.pres-link:disabled, .pres-link[data-disabled="true"] { opacity: 0.4; pointer-events: none; }

.no-results { text-align: center; padding: 3rem; color: var(--text-secondary); }
.link-btn { background: none; border: none; color: var(--color-accent); font: inherit; cursor: pointer; text-decoration: underline; }

/* ----------------------------------------------------------
   MAILING LIST
   ---------------------------------------------------------- */
.section-mailing .section-title { color: #fff; }
.section-mailing .section-title::after { background: rgba(255,255,255,0.4); }

.mail-card {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: var(--border-radius-xl);
  padding: 3.5rem;
  backdrop-filter: blur(10px);
}
.mail-info { color: rgba(255,255,255,0.88); }
.mail-info h2 { color: #fff; margin-bottom: 1rem; text-align: left; }
.mail-info h2::after { margin: 0.75rem 0 0; }
.mail-info p { line-height: 1.7; margin-bottom: 1.5rem; }
.mail-benefits { display: flex; flex-direction: column; gap: 0.75rem; }
.mail-benefits li { font-size: 0.95rem; color: rgba(214,228,247,0.85); }

/* Form */
.mail-form { display: flex; flex-direction: column; gap: 1.25rem; }
.form-group { display: flex; flex-direction: column; gap: 0.4rem; }
.form-label { font-size: 0.88rem; font-weight: 600; color: rgba(255,255,255,0.9); }
.form-input {
  padding: 0.7em 1em;
  border: 1.5px solid rgba(255,255,255,0.25);
  border-radius: var(--border-radius-md);
  background: rgba(255,255,255,0.08);
  color: #fff;
  font-size: 0.95rem;
  transition: border-color var(--transition-fast), background var(--transition-fast), box-shadow var(--transition-fast);
  min-height: 44px;
}
.form-input::placeholder { color: rgba(255,255,255,0.35); }
.form-input:focus {
  outline: none;
  border-color: #7ab8f5;
  background: rgba(255,255,255,0.12);
  box-shadow: 0 0 0 3px rgba(122,184,245,0.2);
}
.form-input.error { border-color: var(--color-error); background: rgba(192,0,0,0.08); }

.radio-group { border: none; }
.radio-group legend { font-size: 0.88rem; font-weight: 600; color: rgba(255,255,255,0.9); margin-bottom: 0.75rem; }
.radio-label {
  display: flex; align-items: center; gap: 0.75rem;
  font-size: 0.9rem; color: rgba(255,255,255,0.85);
  cursor: pointer; padding: 0.6rem 0; min-height: 44px;
}
.radio-label input[type="radio"] { display: none; }
.radio-custom {
  width: 20px; height: 20px; flex-shrink: 0;
  border: 2px solid rgba(255,255,255,0.4);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  transition: border-color var(--transition-fast);
}
.radio-label input[type="radio"]:checked + .radio-custom {
  border-color: #7ab8f5;
  background: radial-gradient(circle, #7ab8f5 40%, transparent 40%);
}

.field-error { font-size: 0.82rem; color: #ff9999; margin-top: 0.15rem; }
.form-feedback {
  padding: 0.85rem 1rem;
  border-radius: var(--border-radius-md);
  font-size: 0.9rem;
  font-weight: 500;
}
.form-feedback.success { background: rgba(30,123,69,0.25); color: #86efac; border: 1px solid rgba(30,123,69,0.35); }
.form-feedback.error   { background: rgba(192,0,0,0.2); color: #fca5a5; border: 1px solid rgba(192,0,0,0.35); }
.form-note { font-size: 0.78rem; color: rgba(255,255,255,0.5); line-height: 1.5; text-align: center; margin-top: 0.25rem; }

/* ----------------------------------------------------------
   ABOUT
   ---------------------------------------------------------- */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: start;
}
.about-text .section-title { text-align: left; }
.about-text .section-title::after { margin: 0.75rem 0 0; }
.about-text p { color: var(--text-secondary); line-height: 1.8; margin-bottom: 1.25rem; }

.about-cards { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.about-card {
  background: var(--bg-section-alt);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 1.5rem 1.25rem;
  text-align: center;
  transition: transform var(--transition-med), box-shadow var(--transition-med);
}
.about-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); }
.about-card-icon { font-size: 2rem; margin-bottom: 0.75rem; }
.about-card h3 { font-size: 0.95rem; font-weight: 700; color: var(--text-primary); margin-bottom: 0.5rem; }
.about-card p { font-size: 0.85rem; color: var(--text-secondary); line-height: 1.6; }
.about-card a { color: var(--color-accent); font-weight: 600; }

/* ----------------------------------------------------------
   FOOTER
   ---------------------------------------------------------- */
.footer {
  background: var(--color-navy);
  padding: 3.5rem 0 0;
}
.footer-inner {
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 3rem;
  align-items: start;
  padding-bottom: 2.5rem;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}
.footer-logo { margin-bottom: 0.5rem; }
.footer-tagline { font-size: 0.82rem; color: rgba(255,255,255,0.45); margin-top: 0.35rem; }
.footer-nav ul { display: flex; flex-direction: column; gap: 0.5rem; }
.footer-nav a { font-size: 0.88rem; color: rgba(255,255,255,0.6); transition: color var(--transition-fast); }
.footer-nav a:hover { color: #fff; }
.footer-social-label { font-size: 0.78rem; font-weight: 600; letter-spacing: 0.08em; text-transform: uppercase; color: rgba(255,255,255,0.4); margin-bottom: 0.75rem; }
.social-links { display: flex; gap: 0.75rem; }
.social-link {
  width: 40px; height: 40px;
  display: flex; align-items: center; justify-content: center;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: var(--border-radius-sm);
  color: rgba(255,255,255,0.6);
  transition: background var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast);
  min-width: 44px; min-height: 44px;
}
.social-link:hover { background: var(--color-accent); border-color: var(--color-accent); color: #fff; }
.footer-bottom {
  padding: 1.25rem 0;
  text-align: center;
  font-size: 0.8rem;
  color: rgba(255,255,255,0.3);
}

/* ----------------------------------------------------------
   BACK TO TOP
   ---------------------------------------------------------- */
.back-to-top {
  position: fixed;
  bottom: 1.75rem;
  right: 1.75rem;
  z-index: 800;
  width: 44px; height: 44px;
  background: var(--color-primary);
  color: #fff;
  border: none;
  border-radius: 50%;
  font-size: 1.1rem;
  box-shadow: var(--shadow-md);
  opacity: 0;
  transform: translateY(12px);
  transition: opacity var(--transition-med), transform var(--transition-med), background var(--transition-fast);
  pointer-events: none;
}
.back-to-top.visible { opacity: 1; transform: translateY(0); pointer-events: auto; }
.back-to-top:hover { background: var(--color-accent); }

/* ----------------------------------------------------------
   RESPONSIVE
   ---------------------------------------------------------- */
@media (max-width: 1024px) {
  .events-grid        { grid-template-columns: repeat(2, 1fr); }
  .presentations-grid { grid-template-columns: repeat(2, 1fr); }
  .about-grid         { grid-template-columns: 1fr; gap: 2.5rem; }
  .mail-card          { grid-template-columns: 1fr; gap: 2.5rem; padding: 2.5rem; }
  .footer-inner       { grid-template-columns: auto auto; }
}

@media (max-width: 768px) {
  :root { --section-pad: 3.5rem; }

  /* Nav mobile */
  .hamburger { display: flex; }
  .nav-links {
    display: none;
    position: fixed;
    top: var(--nav-height);
    left: 0; right: 0;
    background: var(--color-navy);
    border-bottom: 1px solid rgba(255,255,255,0.1);
    flex-direction: column;
    padding: 1rem;
    gap: 0.25rem;
    z-index: 999;
    box-shadow: 0 8px 32px rgba(0,0,0,0.4);
  }
  .nav-links.open { display: flex; }
  .nav-link { padding: 0.75em 1em; border-radius: var(--border-radius-md); }

  .hero-stats { gap: 1.5rem; padding: 1rem 1.25rem; }
  .stat-divider { height: 30px; }
}

@media (max-width: 640px) {
  :root { --section-pad: 2.75rem; }
  .events-grid        { grid-template-columns: 1fr; }
  .presentations-grid { grid-template-columns: 1fr; }
  .about-cards        { grid-template-columns: 1fr; }
  .mail-card          { padding: 1.75rem 1.25rem; gap: 2rem; }
  .footer-inner       { grid-template-columns: 1fr; gap: 2rem; }
  .hero-stats         { flex-direction: column; gap: 1.25rem; }
  .stat-divider       { width: 48px; height: 1px; }
  .hero-ctas          { flex-direction: column; align-items: center; }
  .filter-bar         { flex-direction: column; align-items: flex-start; }
}