/* ============================================================
   PhysicsVault – Global Stylesheet
   style.css — Reset, custom properties, layout, dark/light theme
   ============================================================ */

/* ── Google Fonts ── */
@import url('https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@300;400;500;600;700&family=Source+Serif+4:ital,wght@0,300;0,400;0,600;0,700;1,400&family=JetBrains+Mono:wght@400;500&display=swap');

/* ── CSS Custom Properties ── */
:root {
  /* Colors – dark theme (default) */
  --color-bg:            #0b0d17;
  --color-bg-alt:        #111426;
  --color-bg-card:       #161928;
  --color-bg-elevated:   #1c1f35;
  --color-surface:       #252840;
  --color-border:        #2e3256;
  --color-border-light:  #3d4175;

  --color-text:          #e8eaf6;
  --color-text-muted:    #9095c0;
  --color-text-subtle:   #5e638a;

  --color-primary:       #7c8cff;
  --color-primary-hover: #9daeff;
  --color-primary-dark:  #5a6bff;
  --color-accent:        #f7c948;
  --color-accent-hover:  #ffd96a;
  --color-success:       #4ade80;
  --color-warning:       #fb923c;
  --color-error:         #f87171;
  --color-info:          #38bdf8;

  /* Gradient */
  --gradient-hero:       linear-gradient(135deg, #0b0d17 0%, #0d1530 50%, #130d2a 100%);
  --gradient-card:       linear-gradient(135deg, #161928 0%, #1c1f35 100%);
  --gradient-primary:    linear-gradient(135deg, #5a6bff 0%, #9d6fff 100%);
  --gradient-accent:     linear-gradient(135deg, #f7c948 0%, #ff9d6e 100%);

  /* Typography */
  --font-sans:   'Space Grotesk', system-ui, sans-serif;
  --font-serif:  'Source Serif 4', Georgia, serif;
  --font-mono:   'JetBrains Mono', 'Fira Code', monospace;

  /* Type scale */
  --text-xs:   0.75rem;
  --text-sm:   0.875rem;
  --text-base: 1rem;
  --text-lg:   1.125rem;
  --text-xl:   1.25rem;
  --text-2xl:  1.5rem;
  --text-3xl:  1.875rem;
  --text-4xl:  2.25rem;
  --text-5xl:  3rem;
  --text-6xl:  3.75rem;

  /* Spacing scale */
  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-5:  1.25rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Border radius */
  --radius-sm:   4px;
  --radius-md:   8px;
  --radius-lg:   12px;
  --radius-xl:   16px;
  --radius-2xl:  24px;
  --radius-full: 9999px;

  /* Shadows */
  --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 8px 32px rgba(0,0,0,0.6);
  --shadow-glow: 0 0 30px rgba(124,140,255,0.15);
  --shadow-card: 0 2px 12px rgba(0,0,0,0.5), inset 0 1px 0 rgba(255,255,255,0.04);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;

  /* Layout */
  --max-width:     1280px;
  --nav-height:    68px;
  --sidebar-width: 280px;
}

/* Light theme overrides */
[data-theme="light"] {
  --color-bg:            #f8f9ff;
  --color-bg-alt:        #eef0fb;
  --color-bg-card:       #ffffff;
  --color-bg-elevated:   #f0f2ff;
  --color-surface:       #e8eaf8;
  --color-border:        #d0d4f0;
  --color-border-light:  #b8bde8;

  --color-text:          #1a1c33;
  --color-text-muted:    #4a4e7a;
  --color-text-subtle:   #7a7ea0;

  --color-primary:       #4a5aee;
  --color-primary-hover: #3a4add;
  --color-primary-dark:  #2a3acc;
  --color-accent:        #d4a800;

  --gradient-hero:       linear-gradient(135deg, #eef0fb 0%, #e8ecff 50%, #f0eaff 100%);
  --gradient-card:       linear-gradient(135deg, #ffffff 0%, #f0f2ff 100%);

  --shadow-card: 0 2px 12px rgba(100,110,255,0.08), inset 0 1px 0 rgba(255,255,255,0.8);
  --shadow-glow: 0 0 30px rgba(74,90,238,0.10);
}

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

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

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-slow), color var(--transition-slow);
  overflow-x: hidden;
}

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

/* ── Skip Link ── */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-4);
  padding: var(--space-2) var(--space-4);
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius-md);
  font-weight: 600;
  z-index: 10000;
}
.skip-link:focus { top: var(--space-4); }

/* ── Navigation ── */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 1000;
  height: var(--nav-height);
  background: rgba(11,13,23,0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--color-border);
  transition: background var(--transition-base);
}
[data-theme="light"] .site-nav {
  background: rgba(248,249,255,0.92);
}
.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
  height: 100%;
  display: flex;
  align-items: center;
  gap: var(--space-6);
}
.nav-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
  flex-shrink: 0;
}
.nav-logo-icon {
  width: 36px;
  height: 36px;
}
.nav-logo-text {
  font-size: var(--text-xl);
  font-weight: 700;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  flex: 1;
}
.nav-link {
  padding: var(--space-2) var(--space-3);
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  font-weight: 500;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  white-space: nowrap;
}
.nav-link:hover, .nav-link.active {
  color: var(--color-text);
  background: var(--color-surface);
}

/* Mega Dropdown */
.nav-dropdown { position: relative; }
.nav-dropdown-trigger {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2) var(--space-3);
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  font-weight: 500;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  background: none;
}
.nav-dropdown-trigger:hover, .nav-dropdown.open .nav-dropdown-trigger {
  color: var(--color-text);
  background: var(--color-surface);
}
.nav-dropdown-trigger svg { width: 14px; height: 14px; transition: transform var(--transition-base); }
.nav-dropdown.open .nav-dropdown-trigger svg { transform: rotate(180deg); }

.mega-menu {
  position: absolute;
  top: calc(100% + var(--space-2));
  left: -120px;
  width: 680px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  padding: var(--space-6);
  display: none;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-3);
}
.nav-dropdown.open .mega-menu { display: grid; }
.mega-menu-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-3);
  border-radius: var(--radius-lg);
  transition: background var(--transition-fast);
  text-decoration: none;
}
.mega-menu-item:hover { background: var(--color-surface); }
.mega-menu-icon {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  flex-shrink: 0;
}
.mega-menu-text .mega-menu-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
  display: block;
}
.mega-menu-text .mega-menu-desc {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-top: 2px;
}

/* Nav Right */
.nav-right {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-left: auto;
}
.nav-search-btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  transition: all var(--transition-fast);
}
.nav-search-btn:hover { color: var(--color-text); background: var(--color-surface); }

.theme-toggle {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  background: none;
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast);
}
.theme-toggle:hover { color: var(--color-accent); border-color: var(--color-accent); }

.btn-nav-cta {
  padding: var(--space-2) var(--space-4);
  background: var(--gradient-primary);
  color: white;
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 600;
  white-space: nowrap;
  transition: opacity var(--transition-fast);
}
.btn-nav-cta:hover { opacity: 0.9; color: white; }

/* Mobile hamburger */
.nav-hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 36px;
  height: 36px;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
}
.nav-hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
  transition: all var(--transition-base);
}

/* Mobile Nav */
.mobile-nav {
  position: fixed;
  inset: 0;
  top: var(--nav-height);
  background: var(--color-bg-card);
  z-index: 999;
  padding: var(--space-6);
  overflow-y: auto;
  transform: translateX(100%);
  transition: transform var(--transition-base);
}
.mobile-nav.open { transform: translateX(0); }
.mobile-nav-link {
  display: block;
  padding: var(--space-3) var(--space-4);
  color: var(--color-text);
  font-size: var(--text-lg);
  font-weight: 500;
  border-radius: var(--radius-md);
  border-bottom: 1px solid var(--color-border);
}

/* Search Overlay */
.search-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.8);
  z-index: 2000;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding-top: 100px;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-base);
}
.search-overlay.open { opacity: 1; pointer-events: all; }
.search-modal {
  width: 100%;
  max-width: 680px;
  background: var(--color-bg-card);
  border-radius: var(--radius-xl);
  border: 1px solid var(--color-border);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}
.search-input-wrap {
  display: flex;
  align-items: center;
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--color-border);
  gap: var(--space-3);
}
.search-icon { color: var(--color-text-muted); flex-shrink: 0; }
#search-input {
  flex: 1;
  font-size: var(--text-xl);
  color: var(--color-text);
  background: none;
  border: none;
  outline: none;
}
.search-results { max-height: 400px; overflow-y: auto; }
.search-result-item {
  display: block;
  padding: var(--space-3) var(--space-5);
  border-bottom: 1px solid var(--color-border);
  transition: background var(--transition-fast);
}
.search-result-item:hover { background: var(--color-surface); }
.search-result-item .result-category {
  font-size: var(--text-xs);
  color: var(--color-primary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.search-result-item .result-title {
  font-size: var(--text-base);
  color: var(--color-text);
  font-weight: 500;
}

/* ── Breadcrumb ── */
.breadcrumb {
  background: var(--color-bg-alt);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-3) 0;
}
.breadcrumb-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}
.breadcrumb-list {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-2);
}
.breadcrumb-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}
.breadcrumb-item a { color: var(--color-text-muted); }
.breadcrumb-item a:hover { color: var(--color-primary); }
.breadcrumb-item.current { color: var(--color-text); }
.breadcrumb-sep { color: var(--color-text-subtle); }

/* ── Layout Utilities ── */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}
.section { padding: var(--space-20) 0; }
.section-sm { padding: var(--space-12) 0; }
.section-header { text-align: center; margin-bottom: var(--space-12); }
.section-eyebrow {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-primary);
  margin-bottom: var(--space-3);
  padding: var(--space-1) var(--space-3);
  background: rgba(124,140,255,0.1);
  border-radius: var(--radius-full);
}
.section-title {
  font-size: clamp(var(--text-3xl), 4vw, var(--text-5xl));
  font-weight: 700;
  line-height: 1.1;
  color: var(--color-text);
}
.section-subtitle {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  margin-top: var(--space-4);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* ── Grid Layouts ── */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--space-6); }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-6); }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--space-5); }
.grid-auto { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: var(--space-6); }

/* ── Cards ── */
.card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  box-shadow: var(--shadow-card);
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
}
.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg), var(--shadow-glow);
  border-color: var(--color-border-light);
}
.card-link { text-decoration: none; display: block; }

/* ── Topic Cards ── */
.topic-card {
  background: var(--gradient-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  text-decoration: none;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}
.topic-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--topic-color, var(--gradient-primary));
}
.topic-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border-light);
}
.topic-card-icon {
  font-size: 2.5rem;
  line-height: 1;
}
.topic-card-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-text);
}
.topic-card-desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.5;
}
.topic-card-count {
  font-size: var(--text-xs);
  color: var(--color-primary);
  font-weight: 600;
}
.topic-card-arrow {
  margin-left: auto;
  margin-top: auto;
  color: var(--color-text-muted);
  transition: transform var(--transition-fast);
}
.topic-card:hover .topic-card-arrow { transform: translateX(4px); }

/* ── Article Cards ── */
.article-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  overflow: hidden;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  transition: all var(--transition-base);
}
.article-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border-light);
}
.article-card-thumb {
  aspect-ratio: 16/9;
  background: var(--gradient-card);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  border-bottom: 1px solid var(--color-border);
}
.article-card-body {
  padding: var(--space-5);
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.article-card-category {
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-primary);
}
.article-card-title {
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.3;
}
.article-card-excerpt {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.5;
  flex: 1;
}
.article-card-meta {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  font-size: var(--text-xs);
  color: var(--color-text-subtle);
  margin-top: var(--space-2);
}
.article-card-meta span { display: flex; align-items: center; gap: var(--space-1); }

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 600;
  transition: all var(--transition-fast);
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
}
.btn-primary {
  background: var(--gradient-primary);
  color: white;
  box-shadow: 0 4px 16px rgba(90,107,255,0.3);
}
.btn-primary:hover { opacity: 0.9; transform: translateY(-1px); color: white; }
.btn-secondary {
  background: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
}
.btn-secondary:hover { background: var(--color-bg-elevated); border-color: var(--color-border-light); }
.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}
.btn-outline:hover { background: rgba(124,140,255,0.1); }
.btn-accent {
  background: var(--gradient-accent);
  color: #0b0d17;
  font-weight: 700;
}
.btn-accent:hover { opacity: 0.9; transform: translateY(-1px); }
.btn-lg { padding: var(--space-4) var(--space-8); font-size: var(--text-lg); }
.btn-sm { padding: var(--space-2) var(--space-4); font-size: var(--text-xs); }

/* ── Badges / Tags ── */
.tag {
  display: inline-flex;
  align-items: center;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
  background: rgba(124,140,255,0.12);
  color: var(--color-primary);
  border: 1px solid rgba(124,140,255,0.2);
  text-decoration: none;
  transition: all var(--transition-fast);
}
.tag:hover { background: rgba(124,140,255,0.2); }

/* ── Hero ── */
.hero {
  min-height: 92vh;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
  background: var(--gradient-hero);
}
.hero-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0.6;
}
.hero-content {
  position: relative;
  z-index: 1;
  text-align: center;
  max-width: 900px;
  margin: 0 auto;
  padding: var(--space-20) var(--space-6);
}
.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  background: rgba(124,140,255,0.12);
  border: 1px solid rgba(124,140,255,0.25);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  color: var(--color-primary);
  font-weight: 600;
  margin-bottom: var(--space-6);
}
.hero-title {
  font-size: clamp(2.5rem, 6vw, 5rem);
  font-weight: 800;
  line-height: 1.05;
  color: var(--color-text);
  margin-bottom: var(--space-6);
}
.hero-title .highlight {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-subtitle {
  font-size: clamp(var(--text-lg), 2.5vw, var(--text-xl));
  color: var(--color-text-muted);
  max-width: 680px;
  margin: 0 auto var(--space-8);
  line-height: 1.6;
}
.hero-cta { display: flex; gap: var(--space-4); justify-content: center; flex-wrap: wrap; }
.hero-stats {
  display: flex;
  gap: var(--space-8);
  justify-content: center;
  margin-top: var(--space-12);
  padding-top: var(--space-12);
  border-top: 1px solid var(--color-border);
}
.hero-stat { text-align: center; }
.hero-stat-number {
  font-size: var(--text-3xl);
  font-weight: 800;
  color: var(--color-text);
  display: block;
}
.hero-stat-label {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

/* ── FAQ Accordion ── */
.faq-list { display: flex; flex-direction: column; gap: var(--space-3); }
.faq-item {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.faq-question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--space-6);
  text-align: left;
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--color-text);
  background: none;
  cursor: pointer;
  gap: var(--space-4);
  transition: background var(--transition-fast);
}
.faq-question:hover { background: var(--color-surface); }
.faq-question svg { flex-shrink: 0; transition: transform var(--transition-base); color: var(--color-primary); }
.faq-item.open .faq-question svg { transform: rotate(180deg); }
.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-slow), padding var(--transition-base);
}
.faq-answer-inner {
  padding: 0 var(--space-6) var(--space-5);
  color: var(--color-text-muted);
  line-height: 1.7;
}
.faq-item.open .faq-answer { max-height: 500px; }

/* ── Newsletter ── */
.newsletter-section {
  background: var(--gradient-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-2xl);
  padding: var(--space-16);
  text-align: center;
  position: relative;
  overflow: hidden;
}
.newsletter-form {
  display: flex;
  max-width: 440px;
  margin: var(--space-6) auto 0;
  gap: var(--space-2);
}
.newsletter-input {
  flex: 1;
  padding: var(--space-3) var(--space-4);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  color: var(--color-text);
  font-size: var(--text-sm);
  outline: none;
  transition: border-color var(--transition-fast);
}
.newsletter-input:focus { border-color: var(--color-primary); }

/* ── Formula Tabs ── */
.tabs { display: flex; gap: var(--space-2); flex-wrap: wrap; margin-bottom: var(--space-6); }
.tab-btn {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast);
}
.tab-btn.active {
  background: var(--gradient-primary);
  color: white;
  border-color: transparent;
}
.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* ── Footer ── */
.site-footer {
  background: var(--color-bg-card);
  border-top: 1px solid var(--color-border);
  padding: var(--space-16) 0 var(--space-8);
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr;
  gap: var(--space-12);
  margin-bottom: var(--space-12);
}
.footer-brand .footer-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
  margin-bottom: var(--space-4);
}
.footer-logo-text {
  font-size: var(--text-xl);
  font-weight: 700;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.footer-desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
  max-width: 300px;
}
.footer-col-title {
  font-size: var(--text-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text);
  margin-bottom: var(--space-4);
}
.footer-links { display: flex; flex-direction: column; gap: var(--space-2); }
.footer-link {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}
.footer-link:hover { color: var(--color-primary); }
.footer-bottom {
  border-top: 1px solid var(--color-border);
  padding-top: var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-4);
}
.footer-copy {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}
.footer-bottom-links { display: flex; gap: var(--space-4); }
.footer-bottom-link {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}
.footer-bottom-link:hover { color: var(--color-primary); }

/* ── Responsive ── */
@media (max-width: 1280px) {
  .container { padding: 0 var(--space-5); }
}

@media (max-width: 1024px) {
  .nav-links { display: none; }
  .nav-hamburger { display: flex; }
  .btn-nav-cta { display: none; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
  .mega-menu { width: calc(100vw - var(--space-8)); left: 0; }
}

@media (max-width: 640px) {
  :root { --nav-height: 60px; }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
  .hero-stats { gap: var(--space-6); flex-wrap: wrap; }
  .footer-grid { grid-template-columns: 1fr; gap: var(--space-8); }
  .newsletter-form { flex-direction: column; }
  .section { padding: var(--space-12) 0; }
  .section-title { font-size: var(--text-3xl); }
}

/* ── Utilities ── */
.visually-hidden { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.text-center { text-align: center; }
.text-muted { color: var(--color-text-muted); }
.text-primary { color: var(--color-primary); }
.mt-auto { margin-top: auto; }
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.gap-2 { gap: var(--space-2); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }
.hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }