/* ═══════════════════════════════════════════
   DR. GREEN'S CHEMISTRY DESIGN SYSTEM
   Centralized Stylesheet (index.css)
   ═══════════════════════════════════════════ */

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

:root {
  --navy:       #0d1b2a;
  --navy-mid:   #132233;
  --navy-card:  #1a2e42;
  --navy-border:#1f3a52;
  --amber:      #e8a020;
  --amber-soft: #f5c050;
  --amber-dim:  #b07010;
  --teal:       #2ec4b6;
  --rose:       #e05c5c;
  --slate:      #8ba4bc;
  --slate-light:#b8cfe0;
  --white:      #f0f4f8;
  --text:       #cddaeb;
  --text-dim:   #7a98b4;
  --radius:     6px;
  --radius-lg:  12px;
  --shadow:     0 4px 24px rgba(0,0,0,0.4);
  --font-head:  'Caveat', cursive;
  --font-body:  'Quicksand', sans-serif;
  --font-code:  'Nunito', sans-serif;
}

html { scroll-behavior: smooth; }

body {
  background: url("ib_hub_bg.png") no-repeat center center fixed;
  background-size: cover;
  color: var(--text);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.7;
  min-height: 100vh;
}
/* Overlay for readability on the background pattern */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background: rgba(13, 27, 42, 0.95);
  z-index: -1;
}

/* ═══════════════════════════════════════════
   ANIMATIONS
   ═══════════════════════════════════════════ */
@keyframes fadeUp {
  from { opacity:0; transform:translateY(22px); }
  to   { opacity:1; transform:translateY(0); }
}
@keyframes shimmer {
  0%   { background-position: -200% center; }
  100% { background-position:  200% center; }
}
@keyframes pulse-dot {
  0%,100% { opacity:1; }
  50%      { opacity:0.3; }
}

.fade-up { animation: fadeUp 0.6s ease both; }
.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }

/* ═══════════════════════════════════════════
   GLOBAL NAVIGATION (TOPBAR)
   ═══════════════════════════════════════════ */
.topbar {
  position: sticky; top: 0; z-index: 1000;
  background: rgba(13,27,42,0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--navy-border);
  display: flex; align-items: center;
  padding: 0 2rem;
  height: 72px;
}
.topbar-brand, .logo {
  font-family: var(--font-head);
  font-size: 2.2rem;
  color: var(--white);
  text-decoration: none;
  letter-spacing: 0.02em;
}
.topbar-divider { flex:1; }

.nav-links { display: flex; align-items: center; gap: 1.5rem; list-style: none; height: 100%; }
.nav-links a, .nav-links .dropdown-toggle {
  font-family: var(--font-code);
  text-decoration: none;
  color: var(--text-dim);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  transition: color 0.3s;
  cursor: pointer;
  display: block;
}
.nav-links a:hover, .nav-links a.active, .dropdown:hover .dropdown-toggle { color: var(--teal); }

.dropdown { position: relative; height: 100%; display: flex; align-items: center; }
.dropdown-menu {
  position: absolute; top: 100%; left: 50%;
  transform: translateX(-50%) translateY(10px);
  background: var(--navy-card);
  border: 1px solid var(--navy-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  min-width: 240px;
  padding: 0.75rem 0;
  opacity: 0; visibility: hidden;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  z-index: 1000;
}
.dropdown:hover .dropdown-menu {
  opacity: 1; visibility: visible;
  transform: translateX(-50%) translateY(0);
}
.dropdown-item {
  display: block; padding: 0.6rem 1.2rem;
  color: var(--text-dim); text-decoration: none;
  font-family: var(--font-code); font-size: 0.72rem;
  text-transform: uppercase; letter-spacing: 0.08em;
  transition: background 0.2s, color 0.2s;
}
.dropdown-item:hover { background: rgba(255,255,255,0.05); color: var(--teal); }

/* ═══════════════════════════════════════════
   HERO SECTIONS
   ═══════════════════════════════════════════ */
.hero {
  position: relative;
  overflow: hidden;
  padding: 4rem 2rem; /* Reduced from 8rem */
  border-bottom: 2px solid var(--navy-border);
  background: 
    radial-gradient(circle at 10% 10%, rgba(46, 196, 182, 0.12) 0%, transparent 40%),
    radial-gradient(circle at 90% 90%, rgba(232, 160, 32, 0.08) 0%, transparent 40%),
    linear-gradient(135deg, #0d1b2a 0%, #08121d 100%);
}
.hero::before {
  content: '';
  position: absolute; inset: 0;
  background-image: url("index_hero_bg.png");
  background-size: cover;
  background-position: center;
  pointer-events: none;
  opacity: 0.18; /* Further reduced for 20% more transparency as requested */
  mask-image: radial-gradient(circle at center, black 40%, transparent 95%);
}

/* Home-Specific Hero */
.hero-home {
  padding: 6rem 2rem 5rem;
  text-align: center;
  min-height: 70vh;
  display: flex; align-items: center; justify-content: center;
}
.hero-home .hero-title { font-size: clamp(3.5rem, 9vw, 6rem); }

/* Unit-Specific Hero Decoration */
.hero[data-unit]::after {
  content: attr(data-unit);
  position: absolute; right: 2rem; top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-head);
  font-size: clamp(8rem, 18vw, 14rem);
  font-weight: 700;
  color: rgba(232,160,32,0.05);
  line-height: 1;
  pointer-events: none;
  user-select: none;
}

.hero-inner, .hero-content { max-width: 860px; position: relative; z-index: 10; }
.hero-eyebrow {
  font-family: var(--font-code);
  font-size: 0.82rem;
  letter-spacing: 0.25em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 1.5rem;
  display: flex; align-items: center; justify-content: center; gap: 1.2rem;
}
.hero-eyebrow::before, .hero-eyebrow::after {
  content: '';
  width: 40px; height: 1.5px; background: var(--teal); opacity: 0.4;
}
.hero-title {
  font-family: var(--font-head);
  font-size: clamp(3.5rem, 8vw, 6.5rem);
  color: var(--white);
  line-height: 1;
  margin-bottom: 2rem;
  text-shadow: 0 4px 12px rgba(0,0,0,0.5); /* Added for readability */
}
.hero-subtitle, .hero-motto {
  font-family: var(--font-code);
  font-size: 0.95rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--amber-soft);
  border: 1px solid rgba(232,160,32,0.3);
  padding: 8px 24px;
  border-radius: 100px;
  display: inline-block;
  background: rgba(13, 27, 42, 0.6); /* More opaque background */
  backdrop-filter: blur(5px); /* Added glassmorphism */
}
.hero-home .hero-motto { margin: 0 auto 2rem; }

.hero-meta { display: flex; flex-wrap: wrap; gap: 0.6rem; }
.hero-pill {
  font-family: var(--font-code);
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  padding: 4px 12px;
  border-radius: 100px;
  border: 1px solid;
}
.pill-hl   { color: var(--amber);      border-color: var(--amber-dim);    background: rgba(232,160,32,0.08); }
.pill-sl   { color: var(--teal);       border-color: rgba(46,196,182,0.4); background: rgba(46,196,182,0.07); }
.pill-unit { color: var(--slate-light); border-color: var(--navy-border);  background: var(--navy-card); }

/* Periodic Table Background (Hub Pages) */
.pt-bg-container {
  position: absolute; inset: 0; opacity: 0.03;
  pointer-events: none; overflow: hidden;
  display: flex; align-items: center; justify-content: center;
}
.periodic-table-grid {
  display: grid; grid-template-columns: repeat(18, 1fr);
  grid-template-rows: repeat(10, 1fr); gap: 4px;
  width: 120%; transform: rotate(-5deg) scale(1.2);
}
.pt-cell {
  aspect-ratio: 1; border: 1px solid var(--white);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-code); font-size: 0.8rem; font-weight: 700;
}
.g-alkali { background: var(--amber); color: var(--navy); }
.g-noble  { background: var(--teal); color: var(--navy); }
.g-halogen { background: var(--rose); color: var(--navy); }

/* ═══════════════════════════════════════════
   LAYOUT & CONTAINERS
   ═══════════════════════════════════════════ */
.page-wrap {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2.5rem 2rem 5rem;
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

.about-section {
  max-width: 1000px;
  margin: -40px auto 4rem;
  position: relative;
  z-index: 5;
  padding: 0 2rem;
}

.about-card {
  background: rgba(26, 46, 66, 0.7);
  backdrop-filter: blur(20px);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: var(--radius-lg);
  padding: 3.5rem;
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 3.5rem;
  box-shadow: 0 20px 50px rgba(0,0,0,0.5);
  align-items: center;
}
.about-image-wrap {
  width: 280px; height: 280px;
  border-radius: 50%;
  overflow: hidden;
  border: 6px solid var(--navy-border);
  box-shadow: 0 10px 30px rgba(0,0,0,0.4);
  background: var(--navy-mid);
}
.about-image {
  width: 100%; height: 100%; object-fit: cover;
  filter: grayscale(10%) contrast(1.05);
}
.about-content h2 {
  font-family: var(--font-head);
  font-size: 3.2rem;
  color: var(--white);
  margin-bottom: 1.2rem;
  line-height: 1;
}
.about-text {
  color: var(--text-dim);
  font-size: 1.15rem;
  margin-bottom: 2.5rem;
}
.about-text p { margin-bottom: 1.2rem; }
.about-text strong { color: var(--slate-light); font-weight: 600; }

.section-title {
  font-family: var(--font-head);
  font-size: 2.5rem;
  color: var(--white);
  margin-bottom: 3.5rem;
  text-align: center;
  display: flex; align-items: center; justify-content: center; gap: 2rem;
}
.section-title::before, .section-title::after {
  content: '';
  flex: 1; height: 1.5px; background: var(--navy-border); max-width: 120px;
  opacity: 0.6;
}

/* ═══════════════════════════════════════════
   SECTION BLOCKS & CARDS
   ═══════════════════════════════════════════ */
.section-block {
  background: var(--navy-card);
  border: 1px solid var(--navy-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow);
  scroll-margin-top: 85px;
}
.section-header {
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--navy-border);
  background: rgba(255,255,255,0.02);
}
.section-header-left {
  display: flex; align-items: center; gap: 1rem;
}
.section-label {
  font-family: var(--font-head);
  font-size: 1.8rem;
  color: var(--white);
  font-weight: 600;
}
.vocab-toggle-btn {
  background: rgba(160,110,230,0.15);
  color: var(--white);
  border: 1px solid rgba(160,110,230,0.4);
  padding: 0.5rem 1.25rem;
  border-radius: 100px;
  font-family: var(--font-code);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all 0.3s ease;
}
.vocab-toggle-btn:hover {
  background: rgba(160,110,230,0.25);
  border-color: rgba(160,110,230,0.8);
  transform: translateY(-2px);
}
.vocab-toggle-btn .arrow {
  transition: transform 0.3s ease;
  font-size: 1rem;
}
.vocab-toggle-btn.active .arrow {
  transform: rotate(180deg);
}
.section-body { padding: 1.5rem; }

/* Grid Systems */
.unit-grid, .commons-grid, .resource-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.nav-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2.5rem;
  max-width: 900px;
  margin: 0 auto;
}
@media (max-width: 768px) {
  .nav-grid { grid-template-columns: 1fr; }
}

/* Card Styling */
.nav-card {
  background: var(--navy-card);
  border: 1.5px solid var(--navy-border);
  border-radius: var(--radius-lg);
  padding: 3rem 2rem;
  text-decoration: none;
  transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}
.nav-card:hover {
  border-color: var(--slate);
  transform: translateY(-12px);
  box-shadow: 0 20px 45px rgba(0,0,0,0.5);
  background: rgba(26, 46, 66, 0.95);
}
.nav-card::before {
  content: '';
  position: absolute; inset: 0;
  background: linear-gradient(120deg, transparent, rgba(255, 255, 255, 0.04), transparent);
  transform: translateX(-100%);
  transition: transform 0.8s ease;
}
.nav-card:hover::before { transform: translateX(100%); }

/* Theme Overrides - Match Original Design */
.card-preib .element-icon  { border-color: var(--amber); }
.card-preib .nav-card-title { color: var(--amber); }
.card-preib .atomic-num    { color: var(--amber-dim); }

.card-ib .element-icon     { border-color: var(--teal); }
.card-ib .nav-card-title    { color: var(--teal); }
.card-ib .atomic-num       { color: #26a69a; }

.card-res .element-icon    { border-color: var(--rose); }
.card-res .nav-card-title   { color: var(--rose); }
.card-res .atomic-num      { color: #b71c1c; }

.card-safety .element-icon { border-color: #a855f7; }
.card-safety .nav-card-title{ color: #a855f7; }
.card-safety .atomic-num   { color: #7c3aed; }

/* Tool Card Theme (Restored) */
.card-tools .element-icon  { border-color: #6366f1; }
.card-tools .nav-card-title { color: #6366f1; }
.card-tools .atomic-num    { color: #4338ca; }

.nav-card-title {
  font-family: var(--font-head);
  font-size: 2.2rem;
  margin-bottom: 1.2rem;
}
.nav-card-desc {
  color: var(--text-dim);
  font-size: 0.95rem;
  line-height: 1.6;
}

.res-title { font-family: var(--font-head); font-size: 1.8rem; color: var(--white); margin: 1rem 0 0.5rem; }
.res-desc { font-size: 0.9rem; color: var(--text-dim); line-height: 1.5; }

.commons-thumb { margin-bottom: 1.25rem; }
.commons-info { display: flex; flex-direction: column; gap: 0.5rem; flex: 1; }
.commons-card-title { font-family: var(--font-head); font-size: 1.8rem; color: var(--white); line-height: 1.1; }
.commons-card-desc { font-size: 0.9rem; color: var(--text-dim); line-height: 1.5; }
.commons-links { margin-top: 1rem; display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: center; }
.commons-download, .commons-link {
  font-family: var(--font-code); font-size: 0.75rem; text-transform: uppercase;
  letter-spacing: 0.05em; text-decoration: none; color: var(--teal);
  padding: 4px 10px; border: 1px solid rgba(46, 196, 182, 0.3); border-radius: 4px;
  transition: all 0.2s;
}
.commons-download:hover, .commons-link:hover { background: rgba(46, 196, 182, 0.1); border-color: var(--teal); }

/* Elemental Badges & Icons */
.element-card, .element-icon, .res-icon {
  width: 48px; height: 48px; border: 1.5px solid var(--navy-border);
  border-radius: 6px; background: rgba(255,255,255,0.02);
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  position: relative; line-height: 1; font-family: var(--font-code);
  flex-shrink: 0; transition: transform 0.2s, border-color 0.2s;
}
.res-icon { width: 56px; height: 56px; }
.atomic-num, .res-num { position: absolute; top: 4px; left: 5px; font-size: 0.52rem; color: var(--text-dim); }
.symbol, .res-sym { font-size: 1.35rem; font-weight: 700; color: var(--white); margin-top: 3px; }

/* ═══════════════════════════════════════════
   SPECIALIZED COMPONENTS
   ═══════════════════════════════════════════ */

/* 1. SLIDESHOW */
.slideshow-card {
  display: flex; align-items: stretch; gap: 2.5rem;
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--navy-border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  transition: all 0.3s ease;
  width: 100%;
}
.slideshow-visual {
  width: 140px; height: 180px;
  background: linear-gradient(135deg, var(--navy-card), #2a4a6a);
  border-radius: var(--radius);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0; border: 1px solid var(--navy-border);
}

/* 2. VOCAB FLIP CARDS */
.vocab-container {
  display: none;
  padding: 1.5rem;
  background: rgba(0,0,0,0.1);
  border-bottom: 1px solid var(--navy-border);
}
.vocab-container.expanded {
  display: block;
}
.vocab-grid {
  display: grid !important; 
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)) !important;
  gap: 1.5rem !important; 
  perspective: 1000px;
  width: 100% !important;
}
.vocab-card {
  height: 180px; cursor: pointer; position: relative;
  transform-style: preserve-3d; transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}
.vocab-card.is-flipped { transform: rotateY(180deg); }
.vocab-card-face {
  position: absolute; inset: 0; backface-visibility: hidden;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  padding: 1.5rem; border-radius: var(--radius); border: 2px solid; text-align: center;
}
.vocab-card-front { background: rgba(160,110,230,0.08); border-color: rgba(160,110,230,0.5); }
.vocab-card-back { background: var(--navy-mid); transform: rotateY(180deg); border-color: var(--teal); }

/* 3. VIDEO PLAYSIST */
.video-section {
  background: var(--navy-card); border: 1px solid var(--navy-border);
  border-radius: var(--radius-lg); overflow: hidden; display: flex; flex-direction: column;
}
.video-container-main { display: grid; grid-template-columns: 1fr 340px; background: #000; }
.video-playlist { background: var(--navy-mid); overflow-y: auto; max-height: 500px; }
.playlist-item { padding: 1rem 1.4rem; cursor: pointer; display: flex; gap: 0.8rem; }
.playlist-item.active { background: rgba(46, 196, 182, 0.12); border-left: 4px solid var(--teal); }

/* ═══════════════════════════════════════════
   BUTTONS & LINKS
   ═══════════════════════════════════════════ */
.btn, .cta-button, .slideshow-btn {
  display: inline-flex; align-items: center; gap: 0.6rem;
  padding: 0.75rem 1.8rem; border-radius: 100px;
  font-family: var(--font-code); font-size: 0.82rem; text-transform: uppercase;
  text-decoration: none; transition: all 0.3s ease; font-weight: 700;
}
.btn-primary, .cta-button, .slideshow-btn { background: var(--amber); color: var(--navy); }
.cta-button { background: var(--teal); }
.btn-primary:hover, .cta-button:hover, .slideshow-btn:hover { transform: scale(1.05); }
.cta-button:hover { background: #3ee6d5; box-shadow: 0 12px 24px rgba(46, 196, 182, 0.35); }

.link-item {
  display: flex; align-items: center; gap: 0.75rem;
  padding: 0.7rem 1rem; background: rgba(255,255,255,0.025);
  border: 1px solid var(--navy-border); border-radius: var(--radius);
  text-decoration: none; color: var(--text); transition: all 0.2s;
}
.link-item:hover { background: rgba(255,255,255,0.05); transform: translateX(3px); }

.tag-pdf { background: rgba(224,92,92,0.15); color: #f08080; }

/* ═══════════════════════════════════════════
   FOOTER
   ═══════════════════════════════════════════ */
.footer {
  border-top: 1px solid var(--navy-border);
  padding: 5rem 2rem;
  background: #08111a;
  text-align: center;
}
.footer-content { max-width: 800px; margin: 0 auto; }
.footer-brand {
  font-family: var(--font-head);
  font-size: 2.5rem;
  color: var(--teal);
  margin-bottom: 1.5rem;
}
.footer-links {
  display: flex; justify-content: center; gap: 2.5rem;
  margin-bottom: 2.5rem; list-style: none;
  flex-wrap: wrap;
}
.footer-links a {
  color: var(--text-dim); text-decoration: none; font-size: 0.9rem; 
  font-family: var(--font-code); text-transform: uppercase; letter-spacing: 0.1em;
  transition: color 0.3s;
}
.footer-links a:hover { color: var(--white); }
.footer-copy {
  font-family: var(--font-code);
  font-size: 0.85rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.2em;
}

/* Responsive adjustments */
@media (max-width: 1100px) {
  .video-container-main { grid-template-columns: 1fr; }
  .video-playlist { max-height: 300px; }
}
@media (max-width: 720px) {
  .about-card, .two-col { flex-direction: column; grid-template-columns: 1fr; }
  .topbar { padding: 0 1rem; }
}

/* ═══════════════════════════════════════════ GRADE PREDICTOR CARD */
.card-predictor {
  border: none !important;
}
.card-predictor .element-icon,
.card-predictor .res-icon {
  border: 2px solid var(--amber) !important;
  box-shadow: 0 0 15px rgba(232, 160, 32, 0.2);
}
.card-predictor .symbol {
  color: var(--white) !important;
  text-shadow: 0 0 10px rgba(255, 255, 255, 0.4);
}
.card-predictor .nav-card-title,
.card-predictor .res-title {
  color: var(--amber) !important;
}
.card-predictor .atomic-num {
  color: var(--white) !important;
}
.card-predictor:hover .nav-card-title,
.card-predictor:hover .res-title {
  color: var(--white) !important;
}