/* ================================================================
   edu4.ai Hub - Design System & Styles
   Modern, responsive, professional landing page
   ================================================================ */

/* ── CSS Custom Properties (Design Tokens) ────────────────────── */
:root {
  /* Colors — Ganita green + academic blue palette */
  --color-primary: #0f172a;
  --color-primary-light: #1e293b;
  --color-accent: #349247;
  --color-accent-hover: #2c743c;
  --color-accent-light: #eefcf0;
  --color-accent-secondary: #2f80ed;
  --color-success: #14b8a6;
  --color-warning: #f59e0b;
  --color-danger: #ef4444;

  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-text-inverse: #ffffff;

  --color-bg: #ffffff;
  --color-bg-subtle: #f8fafc;
  --color-bg-muted: #f1f5f9;
  --color-bg-dark: #0f172a;
  --color-bg-dark-subtle: #1e293b;

  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;

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

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

  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.625;

  --tracking-tight: -0.025em;
  --tracking-normal: 0;
  --tracking-wide: 0.025em;

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

  /* Layout */
  --max-width: 1200px;
  --max-width-narrow: 800px;

  /* Borders */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
  --shadow-glow: 0 0 20px rgba(52, 146, 71, 0.15);

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


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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--color-text);
  background: var(--color-bg);
}

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

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

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

ul, ol {
  list-style: none;
}


/* ── Utility Classes ──────────────────────────────────────────── */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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


/* ── Buttons ──────────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-size: var(--text-sm);
  font-weight: 600;
  line-height: var(--leading-tight);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-accent);
  color: var(--color-text-inverse);
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.btn-secondary {
  background: transparent;
  color: var(--color-text);
  border: 1.5px solid var(--color-border);
}

.btn-secondary:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  background: var(--color-accent-light);
}

.btn-ghost {
  background: transparent;
  color: var(--color-text-secondary);
  padding: var(--space-2) var(--space-3);
}

.btn-ghost:hover {
  color: var(--color-accent);
  background: var(--color-bg-muted);
}

.btn-lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-base);
  border-radius: var(--radius-lg);
}

.btn-icon {
  width: 40px;
  height: 40px;
  padding: 0;
  border-radius: var(--radius-md);
}


/* ── Navigation ───────────────────────────────────────────────── */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-light);
  transition: box-shadow var(--transition-base);
}

.nav.scrolled {
  box-shadow: var(--shadow-md);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
  font-size: var(--text-xl);
  color: var(--color-primary);
  letter-spacing: var(--tracking-tight);
}

.nav-brand-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-secondary));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: var(--text-lg);
  font-weight: 800;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav-links a {
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  border-radius: var(--radius-sm);
  transition: color var(--transition-fast), background var(--transition-fast);
}

.nav-links a:hover {
  color: var(--color-accent);
  background: var(--color-bg-muted);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.nav-user {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.nav-user-avatar {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  background: var(--color-accent-light);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  font-size: var(--text-sm);
  color: var(--color-accent);
}

.nav-user-name {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
}

.nav-mobile-toggle {
  display: none;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
}

.nav-mobile-toggle span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  transition: all var(--transition-fast);
  position: relative;
}

.nav-mobile-toggle span::before,
.nav-mobile-toggle span::after {
  content: '';
  position: absolute;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  transition: all var(--transition-fast);
}

.nav-mobile-toggle span::before { top: -6px; }
.nav-mobile-toggle span::after { top: 6px; }


/* ── Hero Section ─────────────────────────────────────────────── */
.hero {
  padding: calc(64px + var(--space-20)) 0 var(--space-20);
  background: linear-gradient(180deg, var(--color-bg) 0%, var(--color-bg-subtle) 100%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -40%;
  right: -20%;
  width: 60%;
  height: 120%;
  background: radial-gradient(ellipse, rgba(52, 146, 71, 0.07) 0%, transparent 70%);
  pointer-events: none;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: -30%;
  left: -10%;
  width: 40%;
  height: 80%;
  background: radial-gradient(ellipse, rgba(47, 128, 237, 0.05) 0%, transparent 70%);
  pointer-events: none;
}

.hero-inner {
  display: flex;
  align-items: center;
  gap: var(--space-16);
  position: relative;
  z-index: 1;
}

.hero-content {
  flex: 1;
  max-width: 600px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-3);
  background: var(--color-accent-light);
  color: var(--color-accent);
  font-size: var(--text-xs);
  font-weight: 600;
  border-radius: var(--radius-full);
  margin-bottom: var(--space-6);
  text-transform: uppercase;
  letter-spacing: var(--tracking-wide);
}

.hero-badge-dot {
  width: 6px;
  height: 6px;
  background: var(--color-success);
  border-radius: var(--radius-full);
  animation: pulse-dot 2s ease infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

.hero h1 {
  font-size: var(--text-5xl);
  font-weight: 800;
  line-height: var(--leading-tight);
  letter-spacing: var(--tracking-tight);
  color: var(--color-primary);
  margin-bottom: var(--space-6);
}

.hero h1 .highlight {
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: var(--text-lg);
  line-height: var(--leading-relaxed);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-8);
  max-width: 520px;
}

.hero-actions {
  display: flex;
  gap: var(--space-4);
  flex-wrap: wrap;
}

.hero-stats {
  display: flex;
  gap: var(--space-8);
  margin-top: var(--space-12);
  padding-top: var(--space-8);
  border-top: 1px solid var(--color-border);
}

.hero-stat {
  flex: 1;
}

.hero-stat-value {
  font-size: var(--text-xl);
  font-weight: 800;
  color: var(--color-accent);
}

.hero-stat-label {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-top: var(--space-1);
  line-height: var(--leading-relaxed);
}

.hero-visual {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

.hero-illustration {
  width: 100%;
  max-width: 440px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

/* App Preview Card */
.hero-app-preview {
  width: 100%;
  background: white;
  border-radius: var(--radius-lg);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.12), 0 0 0 1px rgba(0, 0, 0, 0.04);
  overflow: hidden;
  transform: perspective(800px) rotateY(-2deg) rotateX(1deg);
  transition: transform var(--transition-slow);
}

.hero-app-preview:hover {
  transform: perspective(800px) rotateY(0) rotateX(0);
}

.preview-header {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-border-light);
  background: linear-gradient(to right, var(--color-bg-subtle), white);
}

.preview-header::before {
  content: '';
  display: flex;
  gap: 4px;
}

.preview-dot {
  width: 10px;
  height: 10px;
  border-radius: var(--radius-full);
  background: var(--color-accent);
  box-shadow: 0 0 6px rgba(52, 146, 71, 0.4);
}

.preview-title {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: 0.02em;
}

.preview-input {
  margin: var(--space-4);
  padding: var(--space-3) var(--space-4);
  border: 2px solid var(--color-accent);
  border-radius: var(--radius-md);
  font-family: var(--font-mono, monospace);
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-primary);
  background: var(--color-accent-light);
  letter-spacing: 0.02em;
}

.preview-steps {
  padding: 0 var(--space-4) var(--space-2);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.preview-step {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  background: var(--color-bg-subtle);
}

.preview-step-num {
  width: 26px;
  height: 26px;
  border-radius: var(--radius-full);
  background: var(--color-accent);
  color: white;
  font-size: var(--text-xs);
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.preview-step:last-child {
  background: #eef6ff;
}

.preview-step:last-child .preview-step-num {
  background: var(--color-accent-secondary);
  color: white;
}

.preview-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-3) var(--space-4);
  margin-top: var(--space-3);
  border-top: 1px solid var(--color-border-light);
  background: linear-gradient(to right, var(--color-accent-light), #eef6ff);
}

.preview-xp {
  font-size: var(--text-xs);
  font-weight: 800;
  color: white;
  background: var(--color-accent);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

.preview-streak {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-warning);
}


/* ── Subjects Section ─────────────────────────────────────────── */
.subjects {
  padding: var(--space-24) 0;
}

.section-header {
  text-align: center;
  max-width: var(--max-width-narrow);
  margin: 0 auto var(--space-16);
}

.section-label {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-accent);
  margin-bottom: var(--space-4);
}

.section-title {
  font-size: var(--text-4xl);
  font-weight: 800;
  letter-spacing: var(--tracking-tight);
  color: var(--color-primary);
  margin-bottom: var(--space-4);
}

.section-subtitle {
  font-size: var(--text-lg);
  color: var(--color-text-secondary);
  line-height: var(--leading-relaxed);
}

.subjects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-6);
}

.subject-card {
  position: relative;
  padding: var(--space-8);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: all var(--transition-base);
  overflow: hidden;
}

.subject-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--card-accent, var(--color-accent));
  opacity: 0;
  transition: opacity var(--transition-base);
}

.subject-card:hover {
  border-color: transparent;
  box-shadow: var(--shadow-xl);
  transform: translateY(-4px);
}

.subject-card:hover::before {
  opacity: 1;
}

.subject-card.live {
  cursor: pointer;
}

.subject-card.coming-soon {
  opacity: 0.7;
}

.subject-card-icon {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-2xl);
  margin-bottom: var(--space-5);
  background: var(--card-accent-bg, var(--color-accent-light));
}

.subject-card-badge {
  position: absolute;
  top: var(--space-4);
  right: var(--space-4);
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  font-weight: 600;
  border-radius: var(--radius-full);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.subject-card-badge.badge-live {
  background: #dcfce7;
  color: #15803d;
}

.subject-card-badge.badge-soon {
  background: var(--color-bg-muted);
  color: var(--color-text-muted);
}

.subject-card h3 {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: var(--space-1);
}

.subject-card-subject {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
}

.subject-card p {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-5);
}

.subject-card-action {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-accent);
  transition: gap var(--transition-fast);
}

.subject-card:hover .subject-card-action {
  gap: var(--space-3);
}

.subject-card-action .arrow {
  transition: transform var(--transition-fast);
}

.subject-card:hover .subject-card-action .arrow {
  transform: translateX(4px);
}


/* ── Features Section ─────────────────────────────────────────── */
.features {
  padding: var(--space-24) 0;
  background: var(--color-bg-subtle);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-8);
}

.feature-card {
  text-align: center;
  padding: var(--space-10) var(--space-6);
}

.feature-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto var(--space-6);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-3xl);
  background: var(--color-bg);
  box-shadow: var(--shadow-md);
}

.feature-card h3 {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: var(--space-3);
}

.feature-card p {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: var(--leading-relaxed);
  max-width: 320px;
  margin: 0 auto;
}


/* ── How It Works Section ─────────────────────────────────────── */
.how-it-works {
  padding: var(--space-24) 0;
}

.steps-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-8);
  position: relative;
}

.steps-grid::before {
  content: '';
  position: absolute;
  top: 40px;
  left: 16.6%;
  right: 16.6%;
  height: 2px;
  background: linear-gradient(90deg, var(--color-accent), var(--color-success));
  opacity: 0.3;
}

.step {
  text-align: center;
  position: relative;
}

.step-number {
  width: 48px;
  height: 48px;
  margin: 0 auto var(--space-6);
  border-radius: var(--radius-full);
  background: var(--color-accent);
  color: var(--color-text-inverse);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-lg);
  font-weight: 700;
  position: relative;
  z-index: 1;
}

.step h3 {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: var(--space-3);
}

.step p {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: var(--leading-relaxed);
  max-width: 280px;
  margin: 0 auto;
}


/* ── CTA Section ──────────────────────────────────────────────── */
.cta {
  padding: var(--space-24) 0;
}

.cta-card {
  background: var(--color-bg-dark);
  border-radius: var(--radius-xl);
  padding: var(--space-16) var(--space-12);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.cta-card::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -25%;
  width: 150%;
  height: 200%;
  background: radial-gradient(ellipse, rgba(52, 146, 71, 0.18) 0%, transparent 60%);
  pointer-events: none;
}

.cta-card h2 {
  font-size: var(--text-4xl);
  font-weight: 800;
  color: var(--color-text-inverse);
  margin-bottom: var(--space-4);
  position: relative;
}

.cta-card p {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  margin-bottom: var(--space-8);
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
  position: relative;
}

.cta-card .btn-primary {
  font-size: var(--text-lg);
  padding: var(--space-5) var(--space-10);
  position: relative;
}


/* ── Footer ───────────────────────────────────────────────────── */
.footer {
  padding: var(--space-12) 0;
  border-top: 1px solid var(--color-border);
  background: var(--color-bg);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.footer-brand-icon {
  width: 28px;
  height: 28px;
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-secondary));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: var(--text-xs);
  font-weight: 800;
}

.footer-brand span {
  font-weight: 600;
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
}

.footer-links {
  display: flex;
  gap: var(--space-6);
}

.footer-links a {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-accent);
}

.footer-copy {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}


/* ── SVG Icon System ──────────────────────────────────────────── */
.icon {
  display: inline-flex;
  width: 1em;
  height: 1em;
  fill: currentColor;
}


/* ── Responsive ───────────────────────────────────────────────── */
@media (max-width: 1024px) {
  .hero h1 {
    font-size: var(--text-4xl);
  }

  .hero-visual {
    display: none;
  }

  .hero-inner {
    justify-content: center;
  }

  .hero-content {
    text-align: center;
    max-width: 100%;
  }

  .hero-subtitle {
    margin-left: auto;
    margin-right: auto;
  }

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

  .hero-stats {
    justify-content: center;
  }

  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  :root {
    --text-5xl: 2.25rem;
    --text-4xl: 1.875rem;
    --text-3xl: 1.5rem;
  }

  .nav-links {
    display: none;
  }

  .nav-mobile-toggle {
    display: flex;
  }

  .hero {
    padding: calc(64px + var(--space-12)) 0 var(--space-12);
  }

  .hero-stats {
    flex-direction: column;
    gap: var(--space-4);
    align-items: center;
  }

  .subjects-grid {
    grid-template-columns: 1fr;
    max-width: 400px;
    margin: 0 auto;
  }

  .features-grid,
  .steps-grid {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }

  .steps-grid::before {
    display: none;
  }

  .cta-card {
    padding: var(--space-10) var(--space-6);
  }

  .footer-inner {
    flex-direction: column;
    gap: var(--space-6);
    text-align: center;
  }

  .footer-links {
    flex-wrap: wrap;
    justify-content: center;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-4);
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .hero-actions .btn {
    width: 100%;
    justify-content: center;
  }

  .section-title {
    font-size: var(--text-3xl);
  }
}


/* ================================================================
   SUBJECT PICKER OVERLAY
   Shown after auth — full-screen subject selection
   ================================================================ */

.subject-picker-overlay {
  position: fixed;
  inset: 0;
  z-index: 9999;
  display: flex;
  align-items: center;
  justify-content: center;
  animation: pickerFadeIn 0.3s ease;
}

@keyframes pickerFadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

.subject-picker-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.subject-picker-content {
  position: relative;
  z-index: 1;
  width: 90%;
  max-width: 640px;
  background: var(--color-bg);
  border-radius: 1.5rem;
  padding: 2.5rem 2rem 2rem;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  animation: pickerSlideUp 0.35s ease;
}

@keyframes pickerSlideUp {
  from { opacity: 0; transform: translateY(24px) scale(0.97); }
  to   { opacity: 1; transform: translateY(0) scale(1); }
}

.subject-picker-header {
  text-align: center;
  margin-bottom: 2rem;
}

.subject-picker-avatar {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--color-accent);
  color: white;
  font-size: 1.25rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1rem;
}

.subject-picker-header h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  margin: 0 0 0.25rem;
}

.subject-picker-header p {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  margin: 0;
}

.subject-picker-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.picker-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  padding: 1.25rem 1rem;
  border-radius: 1rem;
  border: 2px solid var(--color-border);
  background: var(--color-bg);
  cursor: pointer;
  transition: all 0.2s ease;
  text-align: center;
  text-decoration: none;
}

.picker-card:hover {
  border-color: var(--card-accent, var(--color-accent));
  background: var(--card-accent-bg, var(--color-accent-light));
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
}

.picker-card.coming-soon {
  opacity: 0.55;
  cursor: default;
}

.picker-card.coming-soon:hover {
  transform: none;
  box-shadow: none;
  border-color: var(--color-border);
  background: var(--color-bg);
}

.picker-card-icon {
  width: 44px;
  height: 44px;
  border-radius: 0.75rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.picker-card h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-text);
  margin: 0;
}

.picker-card .picker-subject {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

.picker-card .picker-badge {
  font-size: 0.65rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
}

.picker-badge.badge-live {
  background: #dcfce7;
  color: #166534;
}

.picker-badge.badge-soon {
  background: var(--color-bg-muted);
  color: var(--color-text-muted);
}

.subject-picker-skip {
  display: block;
  width: 100%;
  padding: 0.75rem;
  border: none;
  background: none;
  color: var(--color-text-muted);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: color 0.2s;
  text-align: center;
}

.subject-picker-skip:hover {
  color: var(--color-text);
}

/* Mobile: single column */
@media (max-width: 480px) {
  .subject-picker-content {
    width: 95%;
    padding: 2rem 1.25rem 1.5rem;
  }
  .subject-picker-grid {
    grid-template-columns: 1fr;
  }
  .subject-picker-header h2 {
    font-size: 1.25rem;
  }
}