/* ══════════════════════════════════════════════════════════════════
   Science Learning Hub — Premium Landing Page CSS
   2026 Scientific Design System · Navy + Cyan + Violet Theme
   Dark + Light Theme · THERABApps
══════════════════════════════════════════════════════════════════ */

/* ─── DARK THEME TOKENS (default) ──────────────────────────────── */
:root {
  /* Backgrounds */
  --bg-primary:        #020b18;
  --bg-secondary:      #050f22;
  --bg-card:           rgba(14,40,90,0.12);
  --bg-card-solid:     #071226;
  --bg-glass:          rgba(2,11,24,0.88);
  --bg-icon:           rgba(0,180,255,0.10);
  --bg-icon-neutral:   rgba(255,255,255,0.05);
  --bg-input:          rgba(255,255,255,0.04);

  /* Borders */
  --border:            rgba(0,180,255,0.18);
  --border-glow:       rgba(0,180,255,0.50);
  --border-subtle:     rgba(255,255,255,0.07);
  --border-card:       rgba(0,180,255,0.14);

  /* Text */
  --text-primary:      #e8f4ff;
  --text-secondary:    #7aaccf;
  --text-muted:        #3a6080;
  --text-on-accent:    #ffffff;

  /* Brand Accents */
  --accent-navy:       #0a1628;
  --accent-blue:       #0066cc;
  --accent-electric:   #00b4ff;
  --accent-cyan:       #00e5ff;
  --accent-violet:     #7c3aed;
  --accent-indigo:     #4f46e5;
  --accent-emerald:    #10b981;
  --accent-silver:     #94a3b8;

  /* Subject colours */
  --physics-color:     #3b82f6;
  --chem-color:        #10b981;
  --bio-color:         #22c55e;
  --earth-color:       #f59e0b;
  --astro-color:       #8b5cf6;

  /* Gradients */
  --grad-primary:      linear-gradient(135deg, #0066cc 0%, #00b4ff 60%, #00e5ff 100%);
  --grad-violet:       linear-gradient(135deg, #7c3aed 0%, #4f46e5 100%);
  --grad-hero:         radial-gradient(ellipse at 60% 40%, rgba(0,180,255,0.08) 0%, transparent 65%), linear-gradient(160deg, #020b18 0%, #050f22 100%);
  --grad-card:         linear-gradient(135deg, rgba(0,180,255,0.06) 0%, rgba(79,70,229,0.06) 100%);
  --grad-download:     radial-gradient(ellipse at 50% 0%, rgba(0,180,255,0.12) 0%, transparent 70%), linear-gradient(160deg, #020b18 0%, #050f22 100%);
  --grad-section-alt:  linear-gradient(160deg, #050f22 0%, #020b18 100%);

  /* Shadows */
  --shadow-glow:       0 0 60px rgba(0,180,255,0.18);
  --shadow-card:       0 8px 32px rgba(0,0,0,0.60);
  --shadow-float:      0 8px 24px rgba(0,0,0,0.50);
  --shadow-nav:        0 4px 24px rgba(0,0,0,0.50);
  --shadow-phone:      0 40px 80px rgba(0,180,255,0.22);
  --shadow-btn:        0 8px 32px rgba(0,180,255,0.35);
  --shadow-formula:    0 4px 20px rgba(0,0,0,0.50);

  /* Radii */
  --radius-sm:   8px;
  --radius-md:   16px;
  --radius-lg:   24px;
  --radius-xl:   32px;
  --radius-full: 9999px;

  /* Transitions */
  --transition:        all 0.3s cubic-bezier(0.4,0,0.2,1);
  --transition-bounce: all 0.4s cubic-bezier(0.34,1.56,0.64,1);
}

/* ─── LIGHT THEME TOKENS ────────────────────────────────────────── */
[data-theme="light"] {
  --bg-primary:        #f0f6ff;
  --bg-secondary:      #e4eeff;
  --bg-card:           rgba(0,102,204,0.05);
  --bg-card-solid:     #ffffff;
  --bg-glass:          rgba(240,246,255,0.94);
  --bg-icon:           rgba(0,102,204,0.10);
  --bg-icon-neutral:   rgba(0,0,0,0.05);
  --bg-input:          rgba(0,0,0,0.04);
  --border:            rgba(0,102,204,0.20);
  --border-glow:       rgba(0,102,204,0.45);
  --border-subtle:     rgba(0,0,0,0.08);
  --border-card:       rgba(0,102,204,0.14);
  --text-primary:      #060e1e;
  --text-secondary:    #1a4a80;
  --text-muted:        #4a6a90;
  --text-on-accent:    #ffffff;
  --accent-navy:       #daeaff;
  --accent-blue:       #005bb5;
  --accent-electric:   #0077cc;
  --accent-cyan:       #0099cc;
  --accent-violet:     #6d28d9;
  --accent-indigo:     #4338ca;
  --accent-emerald:    #059669;
  --accent-silver:     #475569;
  --physics-color:     #2563eb;
  --chem-color:        #059669;
  --bio-color:         #16a34a;
  --earth-color:       #d97706;
  --astro-color:       #7c3aed;
  --grad-primary:      linear-gradient(135deg, #005bb5 0%, #0077cc 60%, #0099cc 100%);
  --grad-violet:       linear-gradient(135deg, #6d28d9 0%, #4338ca 100%);
  --grad-hero:         radial-gradient(ellipse at 60% 40%, rgba(0,102,204,0.08) 0%, transparent 65%), linear-gradient(160deg, #f0f6ff 0%, #e4eeff 100%);
  --grad-card:         linear-gradient(135deg, rgba(0,102,204,0.05) 0%, rgba(67,56,202,0.05) 100%);
  --grad-download:     radial-gradient(ellipse at 50% 0%, rgba(0,102,204,0.08) 0%, transparent 70%), linear-gradient(160deg, #e4eeff 0%, #f0f6ff 100%);
  --grad-section-alt:  linear-gradient(160deg, #e4eeff 0%, #f0f6ff 100%);
  --shadow-glow:       0 0 40px rgba(0,102,204,0.14);
  --shadow-card:       0 4px 20px rgba(0,0,0,0.10);
  --shadow-float:      0 4px 16px rgba(0,0,0,0.10);
  --shadow-nav:        0 2px 16px rgba(0,0,0,0.10);
  --shadow-phone:      0 30px 60px rgba(0,102,204,0.18);
  --shadow-btn:        0 8px 24px rgba(0,102,204,0.30);
  --shadow-formula:    0 4px 16px rgba(0,0,0,0.08);
}

/* ─── RESET & BASE ──────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }
body {
  font-family: 'Outfit', 'Plus Jakarta Sans', 'Inter', sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.65;
  overflow-x: hidden;
  transition: background-color 0.4s ease, color 0.4s ease;
}
img { max-width: 100%; display: block; height: auto; }
a { text-decoration: none; color: inherit; }
ul { list-style: none; }
button { cursor: pointer; border: none; background: none; font-family: inherit; }
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.section-pad { padding: 100px 0; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}

/* ─── SECTION HEADERS ───────────────────────────────────────────── */
.section-header { text-align: center; margin-bottom: 60px; }
.section-eyebrow {
  display: inline-block;
  font-size: 0.75rem; font-weight: 700; letter-spacing: 0.14em;
  text-transform: uppercase; color: var(--accent-electric);
  background: rgba(0,180,255,0.10);
  border: 1px solid rgba(0,180,255,0.22);
  border-radius: var(--radius-full);
  padding: 6px 16px; margin-bottom: 16px;
}
.section-heading {
  font-size: clamp(1.8rem, 4vw, 2.8rem); font-weight: 800;
  line-height: 1.15; color: var(--text-primary);
  margin-bottom: 16px;
}
.section-sub {
  font-size: 1.05rem; color: var(--text-secondary);
  max-width: 600px; margin: 0 auto; line-height: 1.7;
}
.gradient-text {
  background: var(--grad-primary);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ─── BUTTONS ───────────────────────────────────────────────────── */
.btn-primary {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 14px 28px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 1rem; font-weight: 700;
  box-shadow: var(--shadow-btn);
  transition: var(--transition-bounce);
  white-space: nowrap;
}
.btn-primary:hover { transform: translateY(-3px) scale(1.03); box-shadow: 0 16px 40px rgba(0,180,255,0.45); }
.btn-secondary {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 14px 28px; border-radius: var(--radius-full);
  background: transparent; color: var(--accent-electric);
  border: 1.5px solid var(--accent-electric);
  font-size: 1rem; font-weight: 600;
  transition: var(--transition);
}
.btn-secondary:hover { background: rgba(0,180,255,0.08); transform: translateY(-2px); }

/* ─── PRELOADER ─────────────────────────────────────────────────── */
#preloader {
  position: fixed; inset: 0; z-index: 9999;
  background: var(--bg-primary);
  display: flex; align-items: center; justify-content: center;
  transition: opacity 0.5s ease;
}
#preloader.hidden { opacity: 0; pointer-events: none; }
.preloader-inner { text-align: center; }
.preloader-icon {
  font-size: 2.8rem; color: var(--accent-electric);
  margin-bottom: 20px;
  animation: spinAtom 1.8s linear infinite;
}
@keyframes spinAtom { to { transform: rotate(360deg); } }
.preloader-bar {
  width: 200px; height: 3px; background: var(--border);
  border-radius: var(--radius-full); margin: 0 auto 16px; overflow: hidden;
}
.preloader-fill {
  height: 100%; width: 0; background: var(--grad-primary);
  border-radius: var(--radius-full);
  animation: preLoad 1.8s ease forwards;
}
@keyframes preLoad { to { width: 100%; } }
.preloader-text { font-size: 0.85rem; color: var(--text-secondary); letter-spacing: 0.05em; }

/* ─── SCROLL PROGRESS ───────────────────────────────────────────── */
.scroll-progress {
  position: fixed; top: 0; left: 0; height: 3px; width: 0;
  background: var(--grad-primary); z-index: 9998;
  transition: width 0.1s linear;
}

/* ─── NAVBAR ────────────────────────────────────────────────────── */
.navbar {
  position: fixed; top: 0; left: 0; width: 100%; z-index: 900;
  padding: 18px 0;
  transition: var(--transition);
}
.navbar.scrolled {
  background: var(--bg-glass);
  backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-subtle);
  box-shadow: var(--shadow-nav);
  padding: 12px 0;
}
.nav-container {
  max-width: 1200px; margin: 0 auto; padding: 0 24px;
  display: flex; align-items: center; justify-content: space-between; gap: 20px;
}
.nav-logo {
  display: flex; align-items: center; gap: 10px;
  font-size: 1.1rem; font-weight: 800; color: var(--text-primary);
  flex-shrink: 0;
}
.nav-logo-icon { font-size: 1.5rem; color: var(--accent-electric); }
.logo-accent { color: var(--accent-electric); }
.nav-links {
  display: flex; align-items: center; gap: 6px;
  flex-wrap: nowrap;
}
.nav-link {
  padding: 8px 14px; border-radius: var(--radius-full);
  font-size: 0.9rem; font-weight: 500; color: var(--text-secondary);
  transition: var(--transition);
}
.nav-link:hover, .nav-link.active {
  color: var(--accent-electric);
  background: rgba(0,180,255,0.08);
}
.nav-actions { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
.theme-toggle {
  width: 40px; height: 40px; border-radius: var(--radius-full);
  background: var(--bg-icon-neutral); border: 1px solid var(--border-subtle);
  color: var(--text-secondary); font-size: 1rem;
  display: flex; align-items: center; justify-content: center;
  transition: var(--transition);
}
.theme-toggle:hover { color: var(--accent-electric); border-color: var(--accent-electric); }
.btn-nav-download {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 9px 20px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 0.88rem; font-weight: 700;
  box-shadow: var(--shadow-btn);
  transition: var(--transition-bounce);
}
.btn-nav-download:hover { transform: translateY(-2px) scale(1.04); }
.nav-hamburger {
  display: none; flex-direction: column; gap: 5px;
  width: 34px; height: 34px; align-items: center; justify-content: center;
}
.nav-hamburger span {
  display: block; width: 22px; height: 2px;
  background: var(--text-primary); border-radius: 2px;
  transition: var(--transition);
}
.nav-hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-hamburger.open span:nth-child(2) { opacity: 0; }
.nav-hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ─── HERO SECTION ──────────────────────────────────────────────── */
.hero-section {
  position: relative; min-height: 100vh;
  display: flex; align-items: center;
  background: var(--grad-hero);
  overflow: hidden; padding: 120px 0 80px;
}
.hero-particles {
  position: absolute; inset: 0; pointer-events: none; z-index: 0;
}
.hero-bg-orbs { position: absolute; inset: 0; pointer-events: none; z-index: 0; overflow: hidden; }
.orb {
  position: absolute; border-radius: 50%;
  filter: blur(80px); opacity: 0.18;
  animation: floatOrb 12s ease-in-out infinite;
}
.orb-1 { width: 500px; height: 500px; background: var(--accent-blue); top: -100px; right: -80px; animation-delay: 0s; }
.orb-2 { width: 350px; height: 350px; background: var(--accent-violet); bottom: -80px; left: -60px; animation-delay: 4s; }
.orb-3 { width: 280px; height: 280px; background: var(--accent-cyan); top: 40%; left: 40%; animation-delay: 8s; }
@keyframes floatOrb {
  0%,100% { transform: translate(0,0); }
  50% { transform: translate(30px, -30px); }
}
.hero-container {
  position: relative; z-index: 2;
  display: grid; grid-template-columns: 1fr 1fr;
  align-items: center; gap: 60px;
}
.hero-content { max-width: 580px; }
.hero-eyebrow {
  display: flex; flex-wrap: wrap; gap: 6px;
  align-items: center; margin-bottom: 20px;
}
.hero-eyebrow span {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.12em;
  color: var(--accent-electric); text-transform: uppercase;
}
.hero-eyebrow .sep { color: var(--text-muted); }
.hero-heading {
  font-size: clamp(2.4rem, 5.5vw, 4rem); font-weight: 900;
  line-height: 1.1; color: var(--text-primary);
  margin-bottom: 22px;
}
.hero-desc {
  font-size: 1.08rem; color: var(--text-secondary);
  line-height: 1.75; margin-bottom: 36px; max-width: 520px;
}
.hero-ctas { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 32px; }
.hero-badges {
  display: flex; flex-wrap: wrap; gap: 10px;
}
.hero-badge {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 7px 14px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-card);
  font-size: 0.82rem; font-weight: 600; color: var(--text-secondary);
}
.hero-badge i { color: var(--accent-electric); font-size: 0.78rem; }

/* ─── HERO PHONE ────────────────────────────────────────────────── */
.hero-visual { position: relative; display: flex; justify-content: center; align-items: center; }
.hero-phone-wrap { position: relative; z-index: 2; }
.phone-glow {
  position: absolute; inset: -30px; border-radius: 50%;
  background: radial-gradient(circle, rgba(0,180,255,0.22) 0%, transparent 70%);
  filter: blur(30px); pointer-events: none;
}
.phone-mockup {
  width: 280px; background: #0a1628;
  border-radius: 40px; overflow: hidden;
  border: 2px solid rgba(0,180,255,0.35);
  box-shadow: var(--shadow-phone);
  position: relative;
}
.phone-screen { padding: 16px; }
.phone-status-bar {
  display: flex; justify-content: space-between; align-items: center;
  font-size: 0.7rem; color: var(--text-secondary); margin-bottom: 10px; padding: 0 4px;
}
.app-header {
  display: flex; justify-content: space-between; align-items: center;
  padding: 8px 10px; background: rgba(0,180,255,0.06);
  border-radius: var(--radius-md); margin-bottom: 12px;
}
.app-title-small { font-size: 0.78rem; font-weight: 700; color: var(--accent-electric); }
.app-header-icons { display: flex; gap: 10px; color: var(--text-secondary); font-size: 0.8rem; }
.app-body { display: flex; flex-direction: column; gap: 10px; }
.app-continue-card {
  background: rgba(0,180,255,0.08);
  border: 1px solid rgba(0,180,255,0.18);
  border-radius: var(--radius-md); padding: 12px;
}
.app-continue-label { font-size: 0.65rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.1em; margin-bottom: 5px; }
.app-continue-topic { font-size: 0.82rem; font-weight: 700; color: var(--text-primary); margin-bottom: 8px; }
.app-progress-bar {
  height: 4px; background: var(--bg-card); border-radius: var(--radius-full); overflow: hidden; margin-bottom: 4px;
}
.app-progress-fill { height: 100%; background: var(--grad-primary); border-radius: var(--radius-full); }
.app-progress-pct { font-size: 0.68rem; color: var(--accent-electric); font-weight: 700; }
.app-section-label { font-size: 0.65rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.1em; }
.app-subjects-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 5px; }
.app-subj-chip {
  padding: 5px 4px; border-radius: var(--radius-sm);
  font-size: 0.6rem; font-weight: 600; text-align: center;
  border: 1px solid transparent;
}
.chip-physics  { background:rgba(59,130,246,0.15); color:#3b82f6; border-color:rgba(59,130,246,0.25); }
.chip-chem     { background:rgba(16,185,129,0.15); color:#10b981; border-color:rgba(16,185,129,0.25); }
.chip-bio      { background:rgba(34,197,94,0.15);  color:#22c55e; border-color:rgba(34,197,94,0.25); }
.chip-earth    { background:rgba(245,158,11,0.15); color:#f59e0b; border-color:rgba(245,158,11,0.25); }
.chip-astro    { background:rgba(139,92,246,0.15); color:#8b5cf6; border-color:rgba(139,92,246,0.25); }
.app-rec-list { display: flex; flex-direction: column; gap: 4px; }
.app-rec-item { font-size: 0.68rem; color: var(--text-secondary); padding: 5px 8px; background: var(--bg-card); border-radius: var(--radius-sm); }
.app-quick-row { display: grid; grid-template-columns: repeat(4,1fr); gap: 5px; margin-top: 4px; }
.app-quick-btn {
  display: flex; flex-direction: column; align-items: center; gap: 3px;
  padding: 7px 4px; background: var(--bg-card);
  border: 1px solid var(--border-card); border-radius: var(--radius-sm);
  font-size: 0.58rem; color: var(--text-secondary);
}
.app-quick-btn i { font-size: 0.9rem; color: var(--accent-electric); }

/* ─── FLOATING CARDS ────────────────────────────────────────────── */
.float-cards { position: absolute; inset: 0; pointer-events: none; }
.float-card {
  position: absolute; padding: 10px 14px; border-radius: var(--radius-md);
  border: 1px solid var(--border-card); background: var(--bg-glass);
  backdrop-filter: blur(12px); font-size: 0.75rem; font-weight: 600;
  color: var(--text-primary); line-height: 1.5;
  box-shadow: var(--shadow-float);
  animation: floatCard 5s ease-in-out infinite;
}
.float-card small { color: var(--text-secondary); font-weight: 400; }
.fc-physics { top: 5%; left: -30%; animation-delay: 0s; border-color: rgba(59,130,246,0.35); }
.fc-chem    { top: 28%; right: -30%; animation-delay: 1s; border-color: rgba(16,185,129,0.35); }
.fc-bio     { bottom: 30%; left: -28%; animation-delay: 2s; border-color: rgba(34,197,94,0.35); }
.fc-earth   { bottom: 10%; right: -22%; animation-delay: 3s; border-color: rgba(245,158,11,0.35); }
.fc-astro   { top: 55%; left: -35%; animation-delay: 4s; border-color: rgba(139,92,246,0.35); }
@keyframes floatCard {
  0%,100% { transform: translateY(0px); }
  50%     { transform: translateY(-10px); }
}

/* ─── ABOUT SECTION ─────────────────────────────────────────────── */
.about-section { background: var(--bg-secondary); }
.about-cards {
  display: grid; grid-template-columns: repeat(3,1fr); gap: 24px;
  margin-bottom: 40px;
}
.about-card {
  padding: 32px 28px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
  text-align: center;
}
.about-card:hover { transform: translateY(-6px); border-color: var(--accent-electric); box-shadow: var(--shadow-glow); }
.about-card-icon {
  width: 56px; height: 56px; border-radius: var(--radius-full);
  background: var(--bg-icon); color: var(--accent-electric);
  font-size: 1.4rem; display: flex; align-items: center; justify-content: center;
  margin: 0 auto 18px;
}
.about-card h3 { font-size: 1.2rem; font-weight: 700; margin-bottom: 10px; }
.about-card p { font-size: 0.95rem; color: var(--text-secondary); line-height: 1.65; }
.about-audience-row {
  display: flex; flex-wrap: wrap; justify-content: center; gap: 12px;
}
.audience-pill {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 9px 18px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-card);
  font-size: 0.88rem; font-weight: 600; color: var(--text-secondary);
  transition: var(--transition);
}
.audience-pill:hover { color: var(--accent-electric); border-color: var(--accent-electric); background: rgba(0,180,255,0.08); }
.audience-pill i { color: var(--accent-electric); }

/* ─── SUBJECTS BENTO ────────────────────────────────────────────── */
.subjects-section { background: var(--bg-primary); }
.subjects-bento {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: auto auto;
  gap: 20px;
}
.subj-card {
  padding: 28px 24px 20px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card);
  display: flex; flex-direction: column; gap: 14px;
  transition: var(--transition); position: relative; overflow: hidden;
}
.subj-card.large-card { grid-column: span 2; }
.subj-card::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
}
.subj-physics::before { background: var(--physics-color); }
.subj-chem::before    { background: var(--chem-color); }
.subj-bio::before     { background: var(--bio-color); }
.subj-earth::before   { background: var(--earth-color); }
.subj-astro::before   { background: var(--astro-color); }
.subj-card:hover { transform: translateY(-5px); box-shadow: var(--shadow-glow); }
.subj-icon-wrap {
  width: 50px; height: 50px; border-radius: var(--radius-md);
  background: var(--bg-icon); display: flex; align-items: center; justify-content: center;
  font-size: 1.4rem;
}
.subj-physics .subj-icon-wrap { background: rgba(59,130,246,0.12); color: #3b82f6; }
.subj-chem    .subj-icon-wrap { background: rgba(16,185,129,0.12); color: #10b981; }
.subj-bio     .subj-icon-wrap { background: rgba(34,197,94,0.12);  color: #22c55e; }
.subj-earth   .subj-icon-wrap { background: rgba(245,158,11,0.12); color: #f59e0b; }
.subj-astro   .subj-icon-wrap { background: rgba(139,92,246,0.12); color: #8b5cf6; }
.subj-body { flex: 1; }
.subj-title { font-size: 1.1rem; font-weight: 800; margin-bottom: 6px; }
.subj-desc { font-size: 0.9rem; color: var(--text-secondary); margin-bottom: 14px; line-height: 1.6; }
.subj-topics { display: flex; flex-wrap: wrap; gap: 6px; }
.subj-topics span {
  font-size: 0.72rem; padding: 4px 10px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
}
.subj-cta {
  display: inline-flex; align-items: center; gap: 7px;
  font-size: 0.85rem; font-weight: 700; color: var(--accent-electric);
  margin-top: 4px; transition: var(--transition);
}
.subj-cta:hover { gap: 12px; }

/* ─── DASHBOARD SECTION ─────────────────────────────────────────── */
.dashboard-section { background: var(--bg-secondary); }
.dashboard-wrap { display: grid; grid-template-columns: 320px 1fr; gap: 48px; align-items: center; }
.dash-phone-mockup {
  width: 300px; background: #0a1628;
  border-radius: 36px; border: 2px solid rgba(0,180,255,0.30);
  box-shadow: var(--shadow-phone); overflow: hidden;
  flex-shrink: 0;
}
.dash-phone-screen { padding: 18px; }
.dash-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 14px; }
.dash-app-name { font-size: 0.82rem; font-weight: 800; color: var(--accent-electric); }
.dash-header-row { display: flex; gap: 10px; color: var(--text-muted); font-size: 0.8rem; }
.dash-body { display: flex; flex-direction: column; gap: 12px; }
.dash-continue {
  background: rgba(0,180,255,0.08); border: 1px solid rgba(0,180,255,0.18);
  border-radius: var(--radius-md); padding: 12px;
}
.dash-continue-label { font-size: 0.62rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.1em; margin-bottom: 4px; }
.dash-continue-ruler { height: 1px; background: var(--border-subtle); margin: 6px 0; }
.dash-continue-item { display: flex; justify-content: space-between; font-size: 0.8rem; font-weight: 700; color: var(--text-primary); margin-bottom: 6px; }
.dash-pct { color: var(--accent-electric); }
.dash-bar { height: 4px; background: var(--bg-card); border-radius: var(--radius-full); overflow: hidden; }
.dash-bar-fill { height: 100%; background: var(--grad-primary); border-radius: var(--radius-full); }
.dash-rec-label { font-size: 0.62rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.1em; }
.dash-rec-chips { display: flex; flex-wrap: wrap; gap: 4px; }
.dash-rec-chips span {
  font-size: 0.62rem; padding: 3px 8px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
}
.dash-qa-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 6px; }
.dash-qa-btn {
  display: flex; align-items: center; gap: 5px;
  padding: 7px 8px; background: var(--bg-card);
  border: 1px solid var(--border-card); border-radius: var(--radius-sm);
  font-size: 0.62rem; color: var(--text-secondary);
}
.dash-qa-btn i { color: var(--accent-electric); font-size: 0.75rem; }
.dashboard-features { display: flex; flex-direction: column; gap: 16px; }
.df-card {
  display: flex; align-items: flex-start; gap: 16px;
  padding: 18px 20px; border-radius: var(--radius-md);
  background: var(--bg-card); border: 1px solid var(--border-card);
  transition: var(--transition);
}
.df-card:hover { border-color: var(--accent-electric); background: rgba(0,180,255,0.06); }
.df-icon {
  width: 42px; height: 42px; border-radius: var(--radius-md); flex-shrink: 0;
  background: var(--bg-icon); color: var(--accent-electric);
  font-size: 1.1rem; display: flex; align-items: center; justify-content: center;
}
.df-card h4 { font-size: 0.95rem; font-weight: 700; margin-bottom: 3px; }
.df-card p { font-size: 0.85rem; color: var(--text-secondary); line-height: 1.55; }

/* ─── CHAPTERS SECTION ──────────────────────────────────────────── */
.chapters-section { background: var(--bg-primary); }
.chapters-layout { display: flex; flex-direction: column; gap: 24px; }
.chapter-subject-tabs {
  display: flex; flex-wrap: wrap; gap: 8px;
  padding: 6px; background: var(--bg-card); border-radius: var(--radius-full);
  width: fit-content;
}
.ch-tab {
  padding: 10px 20px; border-radius: var(--radius-full);
  font-size: 0.88rem; font-weight: 600; color: var(--text-secondary);
  transition: var(--transition);
}
.ch-tab.active, .ch-tab:hover {
  background: var(--grad-primary); color: #fff;
  box-shadow: 0 4px 16px rgba(0,180,255,0.30);
}
.chapter-list { display: flex; flex-direction: column; gap: 12px; }
.ch-item {
  display: grid; grid-template-columns: 50px 1fr auto;
  align-items: center; gap: 18px;
  padding: 18px 22px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
}
.ch-item:hover { border-color: var(--accent-electric); transform: translateX(4px); }
.ch-num {
  font-size: 1.5rem; font-weight: 900; color: var(--accent-electric);
  opacity: 0.5; font-variant-numeric: tabular-nums;
}
.ch-body h4 { font-size: 1rem; font-weight: 700; margin-bottom: 3px; }
.ch-body p { font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 8px; line-height: 1.5; }
.ch-meta { display: flex; align-items: center; gap: 14px; }
.ch-time { font-size: 0.75rem; color: var(--text-muted); white-space: nowrap; }
.ch-pbar {
  height: 4px; flex: 1; background: var(--bg-card);
  border-radius: var(--radius-full); overflow: hidden; max-width: 100px;
}
.ch-pfill { height: 100%; background: var(--grad-primary); border-radius: var(--radius-full); }
.ch-pct { font-size: 0.75rem; color: var(--accent-electric); font-weight: 700; white-space: nowrap; }
.ch-btn {
  padding: 9px 20px; border-radius: var(--radius-full);
  background: transparent; color: var(--accent-electric);
  border: 1.5px solid var(--accent-electric);
  font-size: 0.82rem; font-weight: 700; white-space: nowrap;
  transition: var(--transition);
}
.ch-btn:hover { background: rgba(0,180,255,0.10); transform: scale(1.05); }

/* ─── CONCEPTS SECTION ──────────────────────────────────────────── */
.concepts-section { background: var(--bg-secondary); }
.concepts-grid {
  display: grid; grid-template-columns: repeat(3,1fr); gap: 24px;
}
.concept-card {
  padding: 28px 22px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); text-align: center;
  transition: var(--transition); overflow: hidden;
}
.concept-card:hover { transform: translateY(-6px); border-color: var(--accent-electric); }
.concept-card h4 { font-size: 1rem; font-weight: 800; margin-bottom: 8px; }
.concept-card p { font-size: 0.88rem; color: var(--text-secondary); line-height: 1.6; }
.cc-arrow { color: var(--accent-electric); font-weight: 700; }
.concept-anim { height: 100px; display: flex; align-items: center; justify-content: center; margin-bottom: 16px; }

/* Atom animation */
.atom-visual { position: relative; width: 80px; height: 80px; }
.nucleus {
  position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%);
  width: 14px; height: 14px; border-radius: 50%;
  background: radial-gradient(circle, var(--accent-cyan), var(--accent-blue));
  box-shadow: 0 0 10px rgba(0,229,255,0.6);
  z-index: 2;
}
.orbit {
  position: absolute; top: 50%; left: 50%;
  border: 1px solid rgba(0,180,255,0.35); border-radius: 50%;
}
.orbit-1 { width: 40px; height: 40px; margin: -20px; animation: orbitSpin 1.5s linear infinite; }
.orbit-2 { width: 60px; height: 60px; margin: -30px; animation: orbitSpin 2.5s linear infinite reverse; transform-origin: center; }
.orbit-3 { width: 78px; height: 78px; margin: -39px; animation: orbitSpin 3.5s linear infinite; }
@keyframes orbitSpin { to { transform: rotate(360deg); } }
.electron {
  position: absolute; width: 6px; height: 6px; border-radius: 50%;
  background: var(--accent-cyan); top: -3px; left: 50%; margin-left: -3px;
  box-shadow: 0 0 6px var(--accent-cyan);
}

/* DNA animation */
.dna-visual { position: relative; display: flex; align-items: center; justify-content: center; }
.dna-strand { display: flex; flex-direction: column; gap: 6px; }
.dna-rung {
  width: 60px; height: 8px; border-radius: 4px;
  background: linear-gradient(90deg, rgba(0,180,255,0.7), rgba(124,58,237,0.7));
  transform: rotateY(calc(var(--i) * 30deg));
  animation: dnaWave 2s ease-in-out infinite;
  animation-delay: calc(var(--i) * 0.15s);
}
@keyframes dnaWave {
  0%,100% { transform: scaleX(1) rotateY(calc(var(--i)*30deg)); }
  50%     { transform: scaleX(0.3) rotateY(calc(var(--i)*30deg)); }
}

/* Earth layers visual */
.earth-layers {
  display: flex; flex-direction: column; gap: 2px;
  width: 90px; border-radius: var(--radius-md); overflow: hidden;
}
.layer {
  padding: 5px 8px; font-size: 0.62rem; font-weight: 700;
  text-align: center; color: #fff;
}
.layer-crust       { background: rgba(139,92,246,0.6); }
.layer-mantle      { background: rgba(245,158,11,0.6); }
.layer-outer       { background: rgba(239,68,68,0.6); }
.layer-inner       { background: rgba(220,38,38,0.8); }

/* Solar mini */
.solar-mini { position: relative; width: 80px; height: 80px; }
.sun-mini { position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); font-size: 1rem; z-index: 2; }
.planet-orb {
  position: absolute; top: 50%; left: 50%;
  width: calc(var(--r) * 2); height: calc(var(--r) * 2);
  margin-left: calc(var(--r) * -1); margin-top: calc(var(--r) * -1);
  border: 1px solid rgba(255,255,255,0.15); border-radius: 50%;
  animation: orbitSpin var(--d) linear infinite;
}
.planet-dot {
  position: absolute; top: -4px; left: 50%; margin-left: -4px;
  width: 8px; height: 8px; border-radius: 50%;
}
.p-mercury { background: #9ca3af; }
.p-venus   { background: #fbbf24; }
.p-earth   { background: #3b82f6; }
.p-mars    { background: #ef4444; }

/* Circuit visual */
.circuit-visual { display: flex; flex-direction: column; align-items: center; gap: 4px; }
.circuit-node {
  width: 32px; height: 32px; border-radius: 50%;
  background: rgba(0,180,255,0.15); border: 2px solid var(--accent-electric);
  display: flex; align-items: center; justify-content: center;
  font-size: 0.8rem; font-weight: 800; color: var(--accent-electric);
}
.circuit-line { width: 2px; height: 12px; background: var(--accent-electric); opacity: 0.5; }

/* Photosynthesis visual */
.photo-visual {
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  font-size: 0.7rem; color: var(--text-secondary); text-align: center;
}
.pv-sun { font-size: 1.2rem; }
.pv-arrow { color: var(--accent-emerald); font-weight: 700; }
.pv-leaf { font-size: 1.2rem; }
.pv-output { font-size: 0.6rem; background: rgba(16,185,129,0.12); padding: 4px 6px; border-radius: 6px; color: var(--accent-emerald); }

/* ─── PHYSICS SECTION ───────────────────────────────────────────── */
.physics-section { background: var(--bg-primary); }
.formula-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 20px; margin-bottom: 36px; }
.formula-card {
  padding: 24px 20px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-formula); transition: var(--transition);
}
.formula-card:hover { border-color: var(--physics-color); transform: translateY(-4px); box-shadow: 0 12px 40px rgba(59,130,246,0.20); }
.formula-badge {
  font-size: 0.72rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em;
  color: var(--physics-color); background: rgba(59,130,246,0.10);
  padding: 4px 10px; border-radius: var(--radius-full);
  display: inline-block; margin-bottom: 12px;
}
.formula-eq {
  font-size: 1.8rem; font-weight: 900; font-family: 'Georgia', serif;
  color: var(--text-primary); margin-bottom: 8px;
  background: var(--grad-primary); -webkit-background-clip: text;
  -webkit-text-fill-color: transparent; background-clip: text;
}
.formula-desc { font-size: 0.85rem; color: var(--text-secondary); margin-bottom: 10px; line-height: 1.5; }
.formula-vars { display: flex; flex-wrap: wrap; gap: 6px; }
.formula-vars span {
  font-size: 0.72rem; padding: 3px 9px; border-radius: var(--radius-full);
  background: rgba(59,130,246,0.08); color: var(--text-secondary);
  border: 1px solid rgba(59,130,246,0.18);
}
.physics-topics { display: flex; flex-wrap: wrap; gap: 8px; }
.phy-topic-chip {
  padding: 7px 16px; border-radius: var(--radius-full);
  background: rgba(59,130,246,0.08); border: 1px solid rgba(59,130,246,0.20);
  font-size: 0.82rem; font-weight: 600; color: var(--physics-color);
  transition: var(--transition);
}
.phy-topic-chip:hover { background: rgba(59,130,246,0.18); }

/* ─── CHEMISTRY SECTION ─────────────────────────────────────────── */
.chemistry-section { background: var(--bg-secondary); }
.chem-layout { display: grid; grid-template-columns: 280px 1fr; gap: 48px; align-items: start; margin-bottom: 36px; }
.chem-hierarchy { display: flex; flex-direction: column; align-items: flex-start; gap: 0; }
.chem-level {
  display: flex; align-items: center; gap: 14px;
  padding: 14px 20px; border-radius: var(--radius-md);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  width: 100%; transition: var(--transition);
}
.chem-level:hover { border-color: var(--chem-color); }
.chl-icon { font-size: 1.3rem; }
.chl-body strong { font-size: 0.95rem; font-weight: 700; display: block; }
.chl-body p { font-size: 0.78rem; color: var(--text-secondary); }
.chem-arrow { color: var(--chem-color); font-size: 1.2rem; font-weight: 700; padding: 2px 0 2px 30px; }
.chem-periodic-preview {
  display: grid; grid-template-columns: repeat(3,1fr); gap: 10px; align-content: start;
}
.pe-card {
  padding: 10px; border-radius: var(--radius-md); text-align: center;
  background: var(--bg-card); border: 1px solid var(--border-card);
  transition: var(--transition);
}
.pe-card:hover { transform: scale(1.06); }
.pe-num { font-size: 0.6rem; color: var(--text-muted); }
.pe-sym { font-size: 1.5rem; font-weight: 900; background: var(--grad-primary); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.pe-name { font-size: 0.6rem; color: var(--text-secondary); }
.pe-more { display: flex; align-items: center; justify-content: center; grid-column: span 3; padding: 12px; font-size: 0.8rem; font-weight: 700; color: var(--accent-electric); background: rgba(0,180,255,0.06); }
.pe-h { border-color: rgba(239,68,68,0.3); }
.pe-he { border-color: rgba(245,158,11,0.3); }
.pe-c { border-color: rgba(107,114,128,0.3); }
.pe-n { border-color: rgba(59,130,246,0.3); }
.pe-o { border-color: rgba(239,68,68,0.3); }
.pe-na { border-color: rgba(250,204,21,0.3); }
.pe-fe { border-color: rgba(161,108,68,0.3); }
.pe-au { border-color: rgba(245,158,11,0.3); }
.chem-topics { display: flex; flex-wrap: wrap; gap: 8px; }
.chem-topic-chip {
  padding: 7px 16px; border-radius: var(--radius-full);
  background: rgba(16,185,129,0.08); border: 1px solid rgba(16,185,129,0.20);
  font-size: 0.82rem; font-weight: 600; color: var(--chem-color);
  transition: var(--transition);
}
.chem-topic-chip:hover { background: rgba(16,185,129,0.18); }

/* ─── BIOLOGY SECTION ───────────────────────────────────────────── */
.biology-section { background: var(--bg-primary); }
.bio-bento {
  display: grid; grid-template-columns: repeat(3,1fr); gap: 20px;
}
.bio-card {
  padding: 26px 22px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
  border-top: 3px solid var(--bio-color);
}
.bio-card:hover { transform: translateY(-5px); box-shadow: 0 12px 40px rgba(34,197,94,0.15); }
.bio-icon { font-size: 2rem; margin-bottom: 12px; }
.bio-card h4 { font-size: 1rem; font-weight: 800; margin-bottom: 8px; }
.bio-card p  { font-size: 0.88rem; color: var(--text-secondary); line-height: 1.65; }

/* ─── EARTH SCIENCE ─────────────────────────────────────────────── */
.earth-section { background: var(--bg-secondary); }
.earth-layout { display: grid; grid-template-columns: 300px 1fr; gap: 48px; align-items: start; }
.earth-globe {
  display: flex; flex-direction: column; gap: 2px;
  border-radius: var(--radius-lg); overflow: hidden;
  box-shadow: var(--shadow-phone); border: 1px solid var(--border-card);
}
.eg-atmosphere { padding: 12px 16px; background: rgba(59,130,246,0.15); font-size: 0.82rem; font-weight: 600; color: #93c5fd; text-align: center; }
.eg-crust      { padding: 14px 16px; background: rgba(139,92,246,0.25); font-size: 0.85rem; font-weight: 700; color: #c4b5fd; text-align: center; }
.eg-mantle     { padding: 22px 16px; background: rgba(245,158,11,0.30); font-size: 0.9rem; font-weight: 700; color: #fcd34d; text-align: center; }
.eg-outer-core { padding: 20px 16px; background: rgba(239,68,68,0.35); font-size: 0.88rem; font-weight: 700; color: #fca5a5; text-align: center; }
.eg-inner-core { padding: 24px 16px; background: rgba(220,38,38,0.50); font-size: 0.9rem; font-weight: 800; color: #fff; text-align: center; }
[data-theme="light"] .eg-atmosphere { color:#1d4ed8; }
[data-theme="light"] .eg-crust      { color:#5b21b6; }
[data-theme="light"] .eg-mantle     { color:#92400e; }
[data-theme="light"] .eg-outer-core { color:#991b1b; }
[data-theme="light"] .eg-inner-core { color:#fff; }
.earth-topics-grid { display: grid; grid-template-columns: repeat(2,1fr); gap: 16px; }
.et-card {
  padding: 20px 18px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
}
.et-card:hover { border-color: var(--earth-color); transform: translateY(-4px); }
.et-icon { font-size: 1.6rem; margin-bottom: 10px; }
.et-card h4 { font-size: 0.95rem; font-weight: 700; margin-bottom: 5px; }
.et-card p  { font-size: 0.83rem; color: var(--text-secondary); line-height: 1.55; }

/* ─── ASTRONOMY SECTION ─────────────────────────────────────────── */
.astronomy-section { background: var(--bg-primary); position: relative; overflow: hidden; }
.star-bg { position: absolute; inset: 0; pointer-events: none; z-index: 0; }
.astro-layout { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; align-items: center; position: relative; z-index: 1; }
.solar-system-vis {
  display: flex; align-items: center; justify-content: center;
  height: 320px;
}
.ss-center { position: relative; width: 280px; height: 280px; }
.ss-sun {
  position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%);
  font-size: 2rem; z-index: 10; display: flex; flex-direction: column; align-items: center;
}
.ss-sun span { font-size: 0.55rem; color: var(--text-muted); }
.ss-orbit {
  position: absolute; top: 50%; left: 50%;
  border: 1px dashed rgba(255,255,255,0.12); border-radius: 50%;
  animation: orbitSpin 8s linear infinite;
}
.so-1 { width: 60px;  height: 60px;  margin:-30px;  animation-duration:3s;  }
.so-2 { width: 90px;  height: 90px;  margin:-45px;  animation-duration:6s;  }
.so-3 { width: 120px; height: 120px; margin:-60px;  animation-duration:10s; }
.so-4 { width: 156px; height: 156px; margin:-78px;  animation-duration:16s; }
.so-5 { width: 198px; height: 198px; margin:-99px;  animation-duration:25s; }
.so-6 { width: 240px; height: 240px; margin:-120px; animation-duration:36s; }
.ss-planet {
  position: absolute; top: -10px; left: 50%; margin-left: -10px;
  width: 20px; height: 20px;
  display: flex; flex-direction: column; align-items: center;
  font-size: 0.65rem;
}
.ss-planet span { font-size: 0.48rem; color: var(--text-muted); white-space: nowrap; }
.sp-mercury { color: #9ca3af; }
.sp-venus   { color: #fbbf24; }
.sp-earth   { color: #3b82f6; }
.sp-mars    { color: #ef4444; }
.sp-jupiter { color: #f97316; font-size: 0.85rem; }
.sp-saturn  { color: #d4a574; font-size: 0.85rem; }
.astro-topics-grid { display: grid; grid-template-columns: repeat(2,1fr); gap: 14px; }
.at-card {
  padding: 18px 16px; border-radius: var(--radius-md);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  transition: var(--transition);
}
.at-card:hover { border-color: var(--astro-color); transform: translateY(-3px); }
.at-icon { font-size: 1.4rem; margin-bottom: 8px; }
.at-card h4 { font-size: 0.92rem; font-weight: 700; margin-bottom: 5px; }
.at-card p  { font-size: 0.8rem; color: var(--text-secondary); line-height: 1.5; }

/* ─── GLOSSARY SECTION ──────────────────────────────────────────── */
.glossary-section { background: var(--bg-secondary); }
.glossary-search-wrap { margin-bottom: 32px; }
.glossary-search {
  display: flex; align-items: center; gap: 14px;
  padding: 14px 20px; border-radius: var(--radius-xl);
  background: var(--bg-card-solid); border: 1.5px solid var(--border-card);
  box-shadow: var(--shadow-card); margin-bottom: 16px;
  transition: var(--transition);
}
.glossary-search:focus-within { border-color: var(--accent-electric); box-shadow: 0 0 0 3px rgba(0,180,255,0.12); }
.glossary-search i { color: var(--text-muted); font-size: 1rem; }
.glossary-search input {
  flex: 1; background: none; border: none; outline: none;
  font-family: inherit; font-size: 1rem; color: var(--text-primary);
}
.glossary-search input::placeholder { color: var(--text-muted); }
.glossary-filter-row { display: flex; flex-wrap: wrap; gap: 8px; }
.gf-btn {
  padding: 8px 18px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-subtle);
  font-size: 0.82rem; font-weight: 600; color: var(--text-secondary);
  transition: var(--transition);
}
.gf-btn.active, .gf-btn:hover {
  background: var(--grad-primary); color: #fff; border-color: transparent;
}
.glossary-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 16px; }
.gloss-card {
  padding: 18px 18px; border-radius: var(--radius-md);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  transition: var(--transition);
}
.gloss-card:hover { border-color: var(--accent-electric); transform: translateY(-3px); }
.gloss-term { font-size: 1rem; font-weight: 800; color: var(--text-primary); margin-bottom: 4px; }
.gloss-subject { font-size: 0.65rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em; padding: 2px 8px; border-radius: var(--radius-full); display: inline-block; margin-bottom: 8px; }
.physics-tag { background: rgba(59,130,246,0.12); color: #3b82f6; }
.chem-tag    { background: rgba(16,185,129,0.12); color: #10b981; }
.bio-tag     { background: rgba(34,197,94,0.12);  color: #22c55e; }
.earth-tag   { background: rgba(245,158,11,0.12); color: #f59e0b; }
.astro-tag   { background: rgba(139,92,246,0.12); color: #8b5cf6; }
.gloss-def { font-size: 0.85rem; color: var(--text-secondary); line-height: 1.6; }

/* ─── FORMULA LIBRARY ───────────────────────────────────────────── */
.formulas-section { background: var(--bg-primary); }
.formula-lib-tabs {
  display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 28px;
  padding: 6px; background: var(--bg-card); border-radius: var(--radius-full);
  width: fit-content;
}
.fl-tab {
  padding: 10px 22px; border-radius: var(--radius-full);
  font-size: 0.88rem; font-weight: 600; color: var(--text-secondary);
  transition: var(--transition);
}
.fl-tab.active, .fl-tab:hover { background: var(--grad-primary); color: #fff; }
.formula-lib-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 18px; }
.fl-card {
  padding: 20px 18px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  transition: var(--transition);
}
.fl-card:hover { border-color: var(--accent-electric); transform: translateY(-3px); }
.fl-subject-badge {
  font-size: 0.68rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em;
  color: var(--accent-electric); background: rgba(0,180,255,0.08);
  padding: 3px 9px; border-radius: var(--radius-full);
  display: inline-block; margin-bottom: 10px;
}
.fl-eq {
  font-size: 1.5rem; font-weight: 900; font-family: 'Georgia', serif;
  color: var(--text-primary); margin-bottom: 6px;
}
.fl-card p { font-size: 0.82rem; color: var(--text-secondary); line-height: 1.5; }

/* ─── QUIZ SECTION ──────────────────────────────────────────────── */
.quiz-section { background: var(--bg-secondary); }
.quiz-layout { display: grid; grid-template-columns: 300px 1fr; gap: 48px; align-items: start; }
.quiz-phone {
  width: 280px; background: #0a1628;
  border-radius: 36px; border: 2px solid rgba(0,180,255,0.30);
  box-shadow: var(--shadow-phone); overflow: hidden; flex-shrink: 0;
}
.quiz-screen { padding: 22px 18px; }
.quiz-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 10px; }
.quiz-subject-badge {
  font-size: 0.68rem; font-weight: 700; padding: 4px 10px; border-radius: var(--radius-full);
  background: rgba(59,130,246,0.15); color: #3b82f6;
}
.quiz-counter { font-size: 0.68rem; color: var(--text-muted); }
.quiz-progress-bar { height: 4px; background: var(--bg-card); border-radius: var(--radius-full); overflow: hidden; margin-bottom: 16px; }
.quiz-progress-fill { height: 100%; background: var(--grad-primary); border-radius: var(--radius-full); }
.quiz-question p { font-size: 0.92rem; font-weight: 700; color: var(--text-primary); margin-bottom: 14px; line-height: 1.5; }
.quiz-options { display: flex; flex-direction: column; gap: 8px; margin-bottom: 16px; }
.qz-opt {
  padding: 10px 14px; border-radius: var(--radius-md);
  background: var(--bg-card); border: 1px solid var(--border-card);
  font-size: 0.82rem; color: var(--text-secondary); transition: var(--transition);
}
.qz-correct { background: rgba(16,185,129,0.15); border-color: #10b981; color: #10b981; font-weight: 700; }
.quiz-submit-btn {
  width: 100%; padding: 11px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 0.88rem; font-weight: 700; margin-bottom: 12px; transition: var(--transition);
}
.quiz-submit-btn:hover { opacity: 0.9; transform: translateY(-1px); }
.quiz-feedback {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 12px; border-radius: var(--radius-md);
  background: rgba(16,185,129,0.10); border: 1px solid rgba(16,185,129,0.25);
}
.correct-fb .fb-icon { color: #10b981; font-size: 1rem; font-weight: 900; margin-top: 1px; }
.fb-text strong { font-size: 0.82rem; color: #10b981; }
.fb-text p { font-size: 0.75rem; color: var(--text-secondary); line-height: 1.5; }
.quiz-features { display: flex; flex-direction: column; gap: 18px; }
.qf-item {
  display: flex; align-items: flex-start; gap: 16px;
  padding: 16px 18px; border-radius: var(--radius-md);
  background: var(--bg-card); border: 1px solid var(--border-card);
  transition: var(--transition);
}
.qf-item:hover { border-color: var(--accent-electric); }
.qf-item i { color: var(--accent-electric); font-size: 1.2rem; flex-shrink: 0; margin-top: 2px; }
.qf-item h4 { font-size: 0.95rem; font-weight: 700; margin-bottom: 3px; }
.qf-item p  { font-size: 0.85rem; color: var(--text-secondary); line-height: 1.5; }

/* ─── REVISION SECTION ──────────────────────────────────────────── */
.revision-section { background: var(--bg-primary); }
.revision-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 20px; }
.rev-card {
  padding: 28px 22px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
}
.rev-card:hover { transform: translateY(-5px); border-color: var(--accent-electric); }
.rev-icon {
  width: 52px; height: 52px; border-radius: var(--radius-full);
  background: var(--bg-icon); color: var(--accent-electric);
  font-size: 1.3rem; display: flex; align-items: center; justify-content: center;
  margin-bottom: 16px;
}
.rev-card h4 { font-size: 1.05rem; font-weight: 800; margin-bottom: 8px; }
.rev-card p  { font-size: 0.88rem; color: var(--text-secondary); line-height: 1.65; }

/* ─── SEARCH SECTION ────────────────────────────────────────────── */
.search-section { background: var(--bg-secondary); }
.search-demo-wrap { max-width: 700px; margin: 0 auto; }
.search-demo-bar {
  display: flex; align-items: center; gap: 14px;
  padding: 18px 24px; border-radius: var(--radius-xl);
  background: var(--bg-card-solid); border: 2px solid var(--accent-electric);
  box-shadow: 0 0 30px rgba(0,180,255,0.15); margin-bottom: 16px;
}
.search-demo-bar i { color: var(--accent-electric); font-size: 1.1rem; }
.search-demo-text { font-size: 1.05rem; font-weight: 600; color: var(--text-primary); flex: 1; }
.search-cursor { color: var(--accent-electric); animation: blink 0.8s step-end infinite; }
@keyframes blink { 50% { opacity: 0; } }
.search-suggestions { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 20px; }
.ss-chip {
  padding: 7px 16px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-subtle);
  font-size: 0.82rem; color: var(--text-secondary); cursor: pointer;
  transition: var(--transition);
}
.ss-chip.active, .ss-chip:hover { background: rgba(0,180,255,0.10); border-color: var(--accent-electric); color: var(--accent-electric); }
.search-results-preview {
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  border-radius: var(--radius-lg); overflow: hidden;
}
.sr-group { padding: 14px 18px; border-bottom: 1px solid var(--border-subtle); }
.sr-group:last-child { border-bottom: none; }
.sr-label { display: flex; align-items: center; gap: 8px; font-size: 0.72rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em; color: var(--text-muted); margin-bottom: 8px; }
.sr-label i { color: var(--accent-electric); }
.sr-item { font-size: 0.88rem; color: var(--text-secondary); padding: 5px 0; border-bottom: 1px solid var(--border-subtle); }
.sr-item:last-child { border-bottom: none; }

/* ─── PROGRESS SECTION ──────────────────────────────────────────── */
.progress-section { background: var(--bg-primary); }
.progress-layout { display: flex; flex-direction: column; gap: 40px; }
.progress-stats-row { display: grid; grid-template-columns: repeat(5,1fr); gap: 20px; }
.ps-card {
  padding: 28px 20px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); text-align: center;
  position: relative; transition: var(--transition);
}
.ps-card:hover { border-color: var(--accent-electric); transform: translateY(-4px); }
.ps-value {
  font-size: 2.4rem; font-weight: 900; color: var(--text-primary);
  background: var(--grad-primary); -webkit-background-clip: text;
  -webkit-text-fill-color: transparent; background-clip: text;
  display: block; line-height: 1.1; margin-bottom: 6px;
}
.ps-unit { font-size: 1.4rem; }
.ps-label { font-size: 0.8rem; color: var(--text-secondary); font-weight: 600; }
.subject-progress-bars {
  padding: 32px; border-radius: var(--radius-xl);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card);
}
.spb-heading { font-size: 1.2rem; font-weight: 800; margin-bottom: 24px; color: var(--text-primary); }
.spb-item { margin-bottom: 20px; }
.spb-label { display: flex; justify-content: space-between; align-items: center; font-size: 0.92rem; font-weight: 600; margin-bottom: 8px; }
.spb-pct { color: var(--accent-electric); font-weight: 800; }
.spb-bar { height: 10px; background: var(--bg-card); border-radius: var(--radius-full); overflow: hidden; }
.spb-fill { height: 100%; border-radius: var(--radius-full); width: var(--w); transition: width 1.2s cubic-bezier(0.4,0,0.2,1); }
.physics-fill { background: linear-gradient(90deg, #2563eb, #3b82f6); }
.chem-fill    { background: linear-gradient(90deg, #059669, #10b981); }
.bio-fill     { background: linear-gradient(90deg, #16a34a, #22c55e); }
.earth-fill   { background: linear-gradient(90deg, #d97706, #f59e0b); }
.astro-fill   { background: linear-gradient(90deg, #7c3aed, #8b5cf6); }

/* ─── AUDIENCE SECTION ──────────────────────────────────────────── */
.audience-section { background: var(--bg-secondary); }
.audience-grid { display: grid; grid-template-columns: repeat(5,1fr); gap: 20px; }
.aud-card {
  padding: 28px 20px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); text-align: center; transition: var(--transition);
}
.aud-card:hover { transform: translateY(-6px); border-color: var(--accent-electric); box-shadow: var(--shadow-glow); }
.aud-icon {
  width: 56px; height: 56px; border-radius: var(--radius-full);
  background: var(--bg-icon); color: var(--accent-electric);
  font-size: 1.4rem; display: flex; align-items: center; justify-content: center;
  margin: 0 auto 16px;
}
.aud-card h4 { font-size: 0.98rem; font-weight: 800; margin-bottom: 8px; }
.aud-card p  { font-size: 0.84rem; color: var(--text-secondary); line-height: 1.6; }

/* ─── JOURNEY SECTION ───────────────────────────────────────────── */
.journey-section { background: var(--bg-primary); }
.journey-steps {
  display: flex; flex-direction: column; align-items: center; gap: 0; max-width: 480px; margin: 0 auto;
}
.jstep {
  display: flex; align-items: flex-start; gap: 20px;
  padding: 24px 28px; border-radius: var(--radius-xl);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); width: 100%; transition: var(--transition);
}
.jstep:hover { border-color: var(--accent-electric); transform: translateX(6px); }
.jstep-num {
  font-size: 2rem; font-weight: 900; color: var(--accent-electric);
  opacity: 0.35; flex-shrink: 0; line-height: 1;
}
.jstep-icon {
  width: 46px; height: 46px; border-radius: var(--radius-md);
  background: var(--bg-icon); color: var(--accent-electric);
  font-size: 1.2rem; display: flex; align-items: center; justify-content: center; flex-shrink: 0;
}
.jstep h4 { font-size: 1.05rem; font-weight: 800; margin-bottom: 4px; }
.jstep p  { font-size: 0.88rem; color: var(--text-secondary); line-height: 1.55; }
.jstep-connector {
  color: var(--accent-electric); font-size: 1.1rem; padding: 6px 0;
  opacity: 0.5;
}

/* ─── COMPARE SECTION ───────────────────────────────────────────── */
.compare-section { background: var(--bg-secondary); }
.compare-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 24px; }
.comp-card {
  padding: 24px 20px; border-radius: var(--radius-xl);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
}
.comp-card:hover { transform: translateY(-4px); border-color: var(--accent-electric); }
.comp-title { font-size: 1rem; font-weight: 800; text-align: center; margin-bottom: 18px; color: var(--text-primary); }
.comp-cols { display: grid; grid-template-columns: 1fr auto 1fr; gap: 10px; align-items: start; }
.comp-label { font-size: 0.78rem; font-weight: 800; color: var(--accent-electric); margin-bottom: 10px; text-align: center; text-transform: uppercase; letter-spacing: 0.08em; }
.comp-col ul { display: flex; flex-direction: column; gap: 6px; }
.comp-col ul li { font-size: 0.8rem; color: var(--text-secondary); padding: 5px 8px; background: var(--bg-card); border-radius: var(--radius-sm); text-align: center; }
.comp-a ul li { border-left: 2px solid var(--physics-color); }
.comp-b ul li { border-right: 2px solid var(--bio-color); }
.comp-vs {
  font-size: 0.8rem; font-weight: 900; color: var(--text-muted);
  padding: 30px 4px 0; text-align: center;
}

/* ─── DAILY SECTION ─────────────────────────────────────────────── */
.daily-section { background: var(--bg-primary); }
.daily-card-wrap { max-width: 680px; margin: 0 auto; }
.daily-fact-card {
  padding: 36px 32px; border-radius: var(--radius-xl);
  background: var(--grad-card);
  border: 1px solid var(--border-glow);
  box-shadow: var(--shadow-glow);
  text-align: center;
}
.daily-badge {
  display: inline-flex; align-items: center; gap: 8px;
  font-size: 0.78rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.12em;
  color: var(--accent-electric); background: rgba(0,180,255,0.10);
  border: 1px solid rgba(0,180,255,0.22);
  padding: 6px 16px; border-radius: var(--radius-full); margin-bottom: 20px;
}
.daily-fact-text {
  font-size: 1.15rem; font-weight: 500; font-style: italic;
  color: var(--text-primary); line-height: 1.8; margin-bottom: 24px;
  border-left: none;
}
.daily-actions { display: flex; justify-content: center; gap: 14px; margin-bottom: 20px; }
.daily-btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 11px 24px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 0.9rem; font-weight: 700; transition: var(--transition-bounce);
}
.daily-btn:hover { transform: scale(1.05); }
.daily-btn-sec {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 11px 24px; border-radius: var(--radius-full);
  background: transparent; color: var(--accent-electric);
  border: 1.5px solid var(--accent-electric);
  font-size: 0.9rem; font-weight: 600; transition: var(--transition);
}
.daily-btn-sec:hover { background: rgba(0,180,255,0.08); }
.daily-related { display: flex; align-items: center; gap: 8px; justify-content: center; flex-wrap: wrap; }
.daily-rel-label { font-size: 0.78rem; color: var(--text-muted); }
.daily-rel-chip {
  padding: 4px 12px; border-radius: var(--radius-full);
  background: var(--bg-card); border: 1px solid var(--border-subtle);
  font-size: 0.78rem; color: var(--text-secondary);
}

/* ─── FEATURES BENTO ────────────────────────────────────────────── */
.features-section { background: var(--bg-secondary); }
.features-bento {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}
.feat-card {
  padding: 26px 22px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
}
.feat-card.feat-large { grid-column: span 2; }
.feat-card:hover { transform: translateY(-5px); }
.feat-icon {
  width: 48px; height: 48px; border-radius: var(--radius-md);
  background: var(--bg-icon); color: var(--accent-electric);
  font-size: 1.2rem; display: flex; align-items: center; justify-content: center;
  margin-bottom: 14px;
}
.feat-card h4 { font-size: 0.98rem; font-weight: 800; margin-bottom: 8px; }
.feat-card p  { font-size: 0.86rem; color: var(--text-secondary); line-height: 1.65; }
.feat-complete { border-top: 3px solid var(--accent-electric); }
.feat-physics  { border-top: 3px solid var(--physics-color); }
.feat-physics .feat-icon  { background: rgba(59,130,246,0.12); color: var(--physics-color); }
.feat-chem     { border-top: 3px solid var(--chem-color); }
.feat-chem .feat-icon     { background: rgba(16,185,129,0.12); color: var(--chem-color); }
.feat-bio      { border-top: 3px solid var(--bio-color); }
.feat-bio .feat-icon      { background: rgba(34,197,94,0.12);  color: var(--bio-color); }
.feat-earth    { border-top: 3px solid var(--earth-color); }
.feat-earth .feat-icon    { background: rgba(245,158,11,0.12); color: var(--earth-color); }
.feat-astro    { border-top: 3px solid var(--astro-color); }
.feat-astro .feat-icon    { background: rgba(139,92,246,0.12); color: var(--astro-color); }
.feat-quiz     { border-top: 3px solid var(--accent-violet); }
.feat-ref      { border-top: 3px solid var(--accent-indigo); }
.feat-ref .feat-icon      { background: rgba(79,70,229,0.12);  color: var(--accent-indigo); }

/* ─── ANDROID SECTION ───────────────────────────────────────────── */
.android-section { background: var(--bg-primary); }
.android-features-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 20px; }
.af-item {
  padding: 24px 20px; border-radius: var(--radius-lg);
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
}
.af-item:hover { border-color: var(--accent-electric); transform: translateY(-4px); }
.af-item i { font-size: 1.5rem; color: var(--accent-electric); margin-bottom: 12px; display: block; }
.af-item h4 { font-size: 0.98rem; font-weight: 800; margin-bottom: 6px; }
.af-item p  { font-size: 0.86rem; color: var(--text-secondary); line-height: 1.6; }

/* ─── SCREENSHOTS ───────────────────────────────────────────────── */
.screenshots-section { background: var(--bg-secondary); }
.screenshots-bento {
  display: grid;
  grid-template-columns: repeat(4,1fr);
  grid-auto-rows: 180px;
  gap: 16px;
}
.sc-card {
  border-radius: var(--radius-lg); overflow: hidden;
  background: var(--bg-card-solid); border: 1px solid var(--border-card);
  box-shadow: var(--shadow-card); transition: var(--transition);
  display: flex; flex-direction: column;
  cursor: default;
}
.sc-card.sc-large { grid-column: span 2; }
.sc-card:hover { transform: scale(1.02); border-color: var(--accent-electric); }
.sc-screen-sim {
  flex: 1; padding: 14px;
  display: flex; flex-direction: column; gap: 6px;
  background: linear-gradient(135deg, #0a1628 0%, #071226 100%);
}
.sc-dark-sim { background: #040d1a; }
.sc-sim-header { display: flex; gap: 5px; margin-bottom: 6px; }
.scs-dot { width: 8px; height: 8px; border-radius: 50%; }
.scs-dot.r { background: #ef4444; } .scs-dot.y { background: #f59e0b; } .scs-dot.g { background: #22c55e; }
.scs-title { font-size: 0.78rem; font-weight: 800; color: var(--accent-electric); }
.scs-formula { font-size: 1.2rem; font-weight: 900; font-family: Georgia,serif; background: var(--grad-primary); -webkit-background-clip:text; -webkit-text-fill-color:transparent; background-clip:text; }
.scs-desc { font-size: 0.65rem; color: var(--text-secondary); }
.scs-bar-wrap { height: 4px; background: var(--bg-card); border-radius: var(--radius-full); overflow:hidden; }
.scs-bar { height:100%; background: var(--grad-primary); border-radius: var(--radius-full); }
.scs-subj-row { display:flex; gap:4px; font-size:0.8rem; }
.scs-chips { display:flex; flex-wrap:wrap; gap:3px; }
.scs-chips span { font-size:0.58rem; padding:2px 6px; border-radius:var(--radius-full); background:rgba(0,180,255,0.1); color:var(--accent-electric); }
.scs-q { font-size:0.75rem; color:var(--text-primary); font-weight:600; margin:4px 0; }
.scs-correct { font-size:0.72rem; color:#10b981; font-weight:700; }
.sc-label {
  padding: 8px 12px; font-size: 0.72rem; font-weight: 700;
  color: var(--text-secondary); background: var(--bg-card);
  border-top: 1px solid var(--border-subtle); text-align: center;
}

/* ─── DOWNLOAD / FINAL CTA ──────────────────────────────────────── */
.download-section {
  position: relative; padding: 120px 0;
  background: var(--grad-download); overflow: hidden;
}
.download-bg-orbs { position: absolute; inset: 0; pointer-events: none; }
.dl-orb { position: absolute; border-radius: 50%; filter: blur(80px); opacity: 0.14; animation: floatOrb 14s ease-in-out infinite; }
.dl-orb-1 { width: 500px; height: 500px; background: var(--accent-blue);   top: -100px; right: -100px; animation-delay: 0s; }
.dl-orb-2 { width: 350px; height: 350px; background: var(--accent-violet); bottom: -80px; left: -80px; animation-delay: 5s; }
.dl-orb-3 { width: 250px; height: 250px; background: var(--accent-cyan);   top: 40%; left: 30%; animation-delay: 10s; }
.download-particles { position: absolute; inset: 0; pointer-events: none; z-index: 0; }
.download-container {
  position: relative; z-index: 2;
  display: grid; grid-template-columns: 1fr 1fr;
  gap: 60px; align-items: center;
}
/* Atom vis in CTA */
.download-science-vis {
  display: flex; align-items: center; justify-content: center; position: relative;
}
.dl-orbit-wrap { position: relative; width: 260px; height: 260px; }
.dl-center-atom { position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); }
.dl-nucleus {
  width: 20px; height: 20px; border-radius: 50%;
  background: radial-gradient(circle, var(--accent-cyan), var(--accent-blue));
  box-shadow: 0 0 20px rgba(0,229,255,0.7);
  position: absolute; top: 50%; left: 50%; transform: translate(-50%,-50%); z-index: 5;
}
.dl-orbit {
  position: absolute; top: 50%; left: 50%;
  border: 1px solid rgba(0,180,255,0.30); border-radius: 50%;
}
.dl-orb-r1 { width: 70px;  height: 70px;  margin:-35px;  animation: orbitSpin 2s linear infinite; }
.dl-orb-r2 { width: 110px; height: 110px; margin:-55px;  animation: orbitSpin 3.5s linear infinite reverse; }
.dl-orb-r3 { width: 150px; height: 150px; margin:-75px;  animation: orbitSpin 5s linear infinite; }
.dl-electron {
  position: absolute; top: -4px; left: 50%; margin-left: -4px;
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--accent-cyan); box-shadow: 0 0 8px var(--accent-cyan);
}
.dl-floating-eq {
  position: absolute; font-size: 0.85rem; font-weight: 800;
  color: var(--accent-electric); opacity: 0.7;
  animation: floatCard 4s ease-in-out infinite;
}
.eq-1 { top: 5%;  left: 60%; animation-delay:0s; }
.eq-2 { top: 65%; left: 60%; animation-delay:1.5s; }
.eq-3 { top: 10%; left: 5%;  animation-delay:0.5s; font-size:1.4rem; }
.eq-4 { top: 70%; left: 5%;  animation-delay:2s;   font-size:1.4rem; }
.eq-5 { top: 40%; left: 80%; animation-delay:1s;   font-size:1.4rem; }
.download-content { max-width: 540px; }
.dl-eyebrow {
  font-size: 0.75rem; font-weight: 700; letter-spacing: 0.14em; text-transform: uppercase;
  color: var(--accent-electric); background: rgba(0,180,255,0.10);
  border: 1px solid rgba(0,180,255,0.22); border-radius: var(--radius-full);
  padding: 6px 16px; display: inline-block; margin-bottom: 20px;
}
.dl-heading { font-size: clamp(2rem,4.5vw,3.2rem); font-weight: 900; line-height: 1.1; margin-bottom: 18px; }
.dl-desc { font-size: 1.05rem; color: var(--text-secondary); line-height: 1.8; margin-bottom: 24px; }
.dl-value-props { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 32px; }
.dl-value-props span {
  font-size: 0.82rem; font-weight: 600; padding: 6px 14px;
  border-radius: var(--radius-full); background: var(--bg-card);
  border: 1px solid var(--border-card); color: var(--text-secondary);
}
.dl-ctas { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 24px; }
.dl-btn-primary {
  display: inline-flex; align-items: center; gap: 12px;
  padding: 16px 28px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 1rem; font-weight: 700; box-shadow: var(--shadow-btn);
  transition: var(--transition-bounce);
}
.dl-btn-primary:hover { transform: translateY(-4px) scale(1.04); box-shadow: 0 20px 50px rgba(0,180,255,0.45); }
.dl-btn-primary span { display: flex; flex-direction: column; line-height: 1.2; }
.dl-btn-primary small { font-size: 0.7rem; font-weight: 400; opacity: 0.85; }
.dl-btn-primary strong { font-size: 1rem; }
.dl-btn-secondary {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 16px 28px; border-radius: var(--radius-full);
  background: transparent; color: var(--accent-electric);
  border: 1.5px solid var(--accent-electric);
  font-size: 1rem; font-weight: 600; transition: var(--transition);
}
.dl-btn-secondary:hover { background: rgba(0,180,255,0.08); transform: translateY(-2px); }
.dl-tagline { font-size: 0.9rem; color: var(--text-muted); font-style: italic; }

/* ─── FOOTER ────────────────────────────────────────────────────── */
.site-footer { background: var(--bg-secondary); border-top: 1px solid var(--border-subtle); }
.footer-top { padding: 64px 0 48px; }
.footer-top-inner { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; }
.footer-logo {
  display: flex; align-items: center; gap: 10px;
  font-size: 1.1rem; font-weight: 800; color: var(--text-primary);
  margin-bottom: 12px;
}
.footer-logo i { color: var(--accent-electric); font-size: 1.3rem; }
.footer-tagline { font-size: 0.9rem; color: var(--text-secondary); margin-bottom: 20px; }
.footer-gplay-btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 20px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 0.88rem; font-weight: 700;
  box-shadow: var(--shadow-btn); transition: var(--transition-bounce);
}
.footer-gplay-btn:hover { transform: translateY(-2px) scale(1.04); }
.footer-col-heading { font-size: 0.82rem; font-weight: 800; text-transform: uppercase; letter-spacing: 0.12em; color: var(--text-primary); margin-bottom: 16px; }
.footer-links-group ul { display: flex; flex-direction: column; gap: 8px; }
.footer-links-group ul li a { font-size: 0.88rem; color: var(--text-secondary); transition: var(--transition); }
.footer-links-group ul li a:hover { color: var(--accent-electric); padding-left: 4px; }
.footer-bottom { padding: 20px 0; border-top: 1px solid var(--border-subtle); }
.footer-bottom-inner { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 8px; }
.footer-bottom p { font-size: 0.82rem; color: var(--text-muted); }
.footer-credits { font-style: italic; }

/* ─── BACK TO TOP ───────────────────────────────────────────────── */
.back-to-top {
  position: fixed; bottom: 28px; right: 28px; z-index: 800;
  width: 48px; height: 48px; border-radius: var(--radius-full);
  background: var(--grad-primary); color: #fff;
  font-size: 1rem; display: flex; align-items: center; justify-content: center;
  box-shadow: var(--shadow-btn);
  opacity: 0; transform: translateY(20px);
  transition: var(--transition);
  pointer-events: none;
}
.back-to-top.visible { opacity: 1; transform: translateY(0); pointer-events: auto; }
.back-to-top:hover { transform: translateY(-4px) scale(1.1); }

/* ─── RESPONSIVE ────────────────────────────────────────────────── */
@media (max-width: 1100px) {
  .hero-container { grid-template-columns: 1fr; gap: 48px; }
  .hero-content { max-width: 100%; text-align: center; }
  .hero-eyebrow, .hero-ctas, .hero-badges { justify-content: center; }
  .hero-visual { justify-content: center; }
  .float-cards { display: none; }

  .subjects-bento { grid-template-columns: repeat(2,1fr); }
  .subj-card.large-card { grid-column: span 1; }

  .dashboard-wrap { grid-template-columns: 1fr; }
  .dash-phone-mockup { margin: 0 auto; }

  .chem-layout { grid-template-columns: 1fr; }
  .chem-periodic-preview { grid-template-columns: repeat(5,1fr); }

  .earth-layout { grid-template-columns: 1fr; }
  .astro-layout { grid-template-columns: 1fr; }
  .solar-system-vis { height: 240px; }

  .quiz-layout { grid-template-columns: 1fr; }
  .quiz-phone { margin: 0 auto; }

  .download-container { grid-template-columns: 1fr; }
  .download-science-vis { display: none; }

  .footer-top-inner { grid-template-columns: 1fr 1fr; gap: 32px; }
  .progress-stats-row { grid-template-columns: repeat(3,1fr); }
  .audience-grid { grid-template-columns: repeat(3,1fr); }

  .features-bento { grid-template-columns: repeat(2,1fr); }
  .feat-card.feat-large { grid-column: span 1; }
}

@media (max-width: 860px) {
  .section-pad { padding: 70px 0; }
  .nav-links { display: none; flex-direction: column; gap: 4px; position: absolute; top: 100%; left: 0; width: 100%; background: var(--bg-glass); backdrop-filter: blur(20px); border-bottom: 1px solid var(--border-subtle); padding: 16px 24px; }
  .nav-links.open { display: flex; }
  .nav-hamburger { display: flex; }
  .navbar { padding: 14px 0; }
  .nav-container { position: relative; }

  .about-cards { grid-template-columns: 1fr; }
  .subjects-bento { grid-template-columns: 1fr; }
  .formula-grid { grid-template-columns: repeat(2,1fr); }
  .concepts-grid { grid-template-columns: repeat(2,1fr); }
  .bio-bento { grid-template-columns: repeat(2,1fr); }
  .earth-topics-grid { grid-template-columns: 1fr; }
  .astro-topics-grid { grid-template-columns: 1fr; }
  .glossary-grid { grid-template-columns: repeat(2,1fr); }
  .formula-lib-grid { grid-template-columns: repeat(2,1fr); }
  .revision-grid { grid-template-columns: repeat(2,1fr); }
  .compare-grid { grid-template-columns: 1fr; }
  .audience-grid { grid-template-columns: repeat(2,1fr); }
  .android-features-grid { grid-template-columns: repeat(2,1fr); }
  .screenshots-bento { grid-template-columns: repeat(2,1fr); }
  .sc-card.sc-large { grid-column: span 1; }
  .features-bento { grid-template-columns: 1fr; }
  .feat-card.feat-large { grid-column: span 1; }

  .chapter-subject-tabs { width: 100%; border-radius: var(--radius-xl); justify-content: flex-start; overflow-x: auto; }
  .progress-stats-row { grid-template-columns: repeat(2,1fr); }
}

@media (max-width: 560px) {
  .section-pad { padding: 56px 0; }
  .container { padding: 0 16px; }
  .hero-heading { font-size: 2.2rem; }
  .hero-eyebrow { font-size: 0.62rem; }
  .hero-ctas { flex-direction: column; align-items: center; }
  .btn-primary, .btn-secondary { width: 100%; max-width: 320px; justify-content: center; }
  .phone-mockup { width: 240px; }
  .formula-grid { grid-template-columns: 1fr; }
  .concepts-grid { grid-template-columns: 1fr; }
  .bio-bento { grid-template-columns: 1fr; }
  .glossary-grid { grid-template-columns: 1fr; }
  .formula-lib-grid { grid-template-columns: 1fr; }
  .revision-grid { grid-template-columns: 1fr; }
  .audience-grid { grid-template-columns: 1fr; }
  .android-features-grid { grid-template-columns: 1fr; }
  .screenshots-bento { grid-template-columns: 1fr; }
  .footer-top-inner { grid-template-columns: 1fr; }
  .footer-bottom-inner { flex-direction: column; text-align: center; }
  .ch-item { grid-template-columns: 40px 1fr; }
  .ch-btn { grid-column: 2; width: 100%; }
  .progress-stats-row { grid-template-columns: repeat(2,1fr); }
  .dl-ctas { flex-direction: column; align-items: flex-start; }
  .dl-btn-primary, .dl-btn-secondary { width: 100%; max-width: 320px; justify-content: center; }
  .section-heading { font-size: 1.7rem; }
}

/* ─── REDUCED MOTION ────────────────────────────────────────────── */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; }
  html { scroll-behavior: auto; }
}

/* ─── FOCUS STYLES ──────────────────────────────────────────────── */
:focus-visible {
  outline: 2px solid var(--accent-electric);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ─── SCROLLBAR ─────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-primary); }
::-webkit-scrollbar-thumb { background: var(--accent-blue); border-radius: var(--radius-full); }
::-webkit-scrollbar-thumb:hover { background: var(--accent-electric); }

/* ─── SELECTION ─────────────────────────────────────────────────── */
::selection { background: rgba(0,180,255,0.25); color: var(--text-primary); }