/* ============================================================
   SCIENCE FOR LITTLE STARS — Global Design System
   Clean white base + vibrant color pops per chapter
   Font: Nunito (headings) + DM Sans (body)
   ============================================================ */

/* ---------- Google Fonts import ---------- */
@import url('https://fonts.googleapis.com/css2?family=Nunito:wght@400;600;700;800;900&family=DM+Sans:wght@400;500;600&display=swap');

/* ---------- CSS Custom Properties (Design Tokens) ---------- */
:root {
  --white: #ffffff;
  --off-white: #f8f9ff;
  --gray-100: #f1f3f9;
  --gray-200: #e2e6f0;
  --gray-500: #8892a4;
  --gray-800: #1e2a3a;
  --text: #1e2a3a;
  --text-light: #5a6a7e;

  /* Chapter accent colors */
  --solar:    #ff6b35;
  --plants:   #3cb35a;
  --animals:  #f59e0b;
  --senses:   #8b5cf6;
  --magnets:  #2563eb;
  --weather:  #06b6d4;
  --machines: #ef4444;
  --body:     #ec4899;
  --energy:   #d97706;
  --planet:   #0d9488;

  /* Current chapter color (overridden per page) */
  --accent: #3cb35a;
  --accent-light: #d1fae5;

  /* Typography scale */
  --text-xs:  clamp(0.7rem, 1.5vw, 0.8rem);
  --text-sm:  clamp(0.85rem, 2vw, 0.95rem);
  --text-base:clamp(1rem, 2.5vw, 1.1rem);
  --text-lg:  clamp(1.1rem, 3vw, 1.3rem);
  --text-xl:  clamp(1.25rem, 4vw, 1.6rem);
  --text-2xl: clamp(1.5rem, 5vw, 2rem);
  --text-3xl: clamp(1.8rem, 6vw, 2.6rem);
  --text-4xl: clamp(2.2rem, 7vw, 3.4rem);

  /* Spacing */
  --space-xs:  0.4rem;
  --space-sm:  0.75rem;
  --space-md:  1.25rem;
  --space-lg:  2rem;
  --space-xl:  3rem;
  --space-2xl: 5rem;

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

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.12);
  --shadow-accent: 0 8px 30px rgba(0,0,0,0.15);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'DM Sans', sans-serif;
  background: var(--white);
  color: var(--text);
  font-size: var(--text-base);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5 {
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  line-height: 1.2;
  color: var(--text);
}

a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }
ul { list-style: none; }

/* ---------- Global Utility Classes ---------- */
.container {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.section { padding: var(--space-2xl) 0; }
.section--sm { padding: var(--space-xl) 0; }

.text-accent { color: var(--accent); }
.text-center { text-align: center; }
.text-light { color: var(--text-light); }

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.9rem;
  border-radius: var(--radius-full);
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  background: var(--accent-light);
  color: var(--accent);
}

/* ---------- NAVIGATION ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 2px solid var(--gray-100);
  padding: 0 var(--space-lg);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1100px;
  margin: 0 auto;
  height: 64px;
}

/* Logo in nav */
.nav__logo {
  font-family: 'Nunito', sans-serif;
  font-weight: 900;
  font-size: var(--text-lg);
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.nav__logo span {
  color: var(--accent); /* star icon pops in accent color */
}

/* Desktop nav links */
.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.nav__links a {
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--text-light);
  transition: color 0.2s;
  padding: 0.4rem 0.2rem;
  border-bottom: 2px solid transparent;
}

.nav__links a:hover, .nav__links a.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

/* Quiz CTA button in nav */
.nav__cta {
  background: var(--accent);
  color: #fff !important;
  padding: 0.5rem 1.2rem !important;
  border-radius: var(--radius-full) !important;
  border-bottom: none !important;
  transition: transform 0.2s, box-shadow 0.2s !important;
}

.nav__cta:hover {
  transform: translateY(-2px) !important;
  box-shadow: 0 4px 16px rgba(0,0,0,0.2) !important;
}

/* Mobile hamburger */
.nav__hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
}

.nav__hamburger span {
  display: block;
  width: 24px;
  height: 2.5px;
  background: var(--text);
  border-radius: 2px;
  transition: all 0.3s;
}

/* Mobile menu */
.nav__mobile {
  display: none;
  flex-direction: column;
  gap: var(--space-sm);
  background: var(--white);
  padding: var(--space-md) var(--space-lg) var(--space-lg);
  border-top: 1px solid var(--gray-100);
}

.nav__mobile a {
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-base);
  color: var(--text);
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--gray-100);
  display: block;
}

.nav__mobile a:last-child { border-bottom: none; }
.nav__mobile.open { display: flex; }

/* ---------- HERO SECTION (Home) ---------- */
.hero {
  padding: var(--space-2xl) var(--space-lg) var(--space-xl);
  text-align: center;
  background: var(--off-white);
  position: relative;
  overflow: hidden;
}

/* Decorative background blobs */
.hero::before {
  content: '';
  position: absolute;
  width: 500px; height: 500px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(60,179,90,0.12), transparent 70%);
  top: -100px; left: -100px;
  pointer-events: none;
}

.hero::after {
  content: '';
  position: absolute;
  width: 400px; height: 400px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(255,107,53,0.1), transparent 70%);
  bottom: -80px; right: -80px;
  pointer-events: none;
}

.hero__emoji {
  font-size: clamp(3rem, 8vw, 5rem);
  margin-bottom: var(--space-md);
  display: block;
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50%       { transform: translateY(-12px); }
}

.hero__title {
  font-size: var(--text-4xl);
  margin-bottom: var(--space-sm);
  background: linear-gradient(135deg, var(--text) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero__sub {
  font-size: var(--text-lg);
  color: var(--text-light);
  max-width: 520px;
  margin: 0 auto var(--space-lg);
}

.hero__buttons {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
  flex-wrap: wrap;
}

/* ---------- BUTTONS ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-base);
  padding: 0.75rem 1.75rem;
  border-radius: var(--radius-full);
  cursor: pointer;
  border: none;
  transition: transform 0.2s, box-shadow 0.2s;
  text-decoration: none;
}

.btn:hover { transform: translateY(-3px); box-shadow: var(--shadow-accent); }
.btn:active { transform: translateY(0); }

.btn--primary {
  background: var(--accent);
  color: #fff;
}

.btn--outline {
  background: transparent;
  color: var(--accent);
  border: 2.5px solid var(--accent);
}

.btn--white {
  background: var(--white);
  color: var(--accent);
}

/* ---------- CHAPTER CARDS (Home grid) ---------- */
.chapters-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-md);
}

.chapter-card {
  background: var(--white);
  border: 2px solid var(--gray-100);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  transition: transform 0.25s, box-shadow 0.25s, border-color 0.25s;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  text-decoration: none;
  color: inherit;
}

.chapter-card::before {
  /* colored top bar */
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: var(--card-color, var(--accent));
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.chapter-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
  border-color: var(--card-color, var(--accent));
}

.chapter-card__num {
  font-family: 'Nunito', sans-serif;
  font-weight: 900;
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--card-color, var(--accent));
}

.chapter-card__icon {
  font-size: 2.8rem;
  line-height: 1;
}

.chapter-card__title {
  font-size: var(--text-xl);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
}

.chapter-card__desc {
  font-size: var(--text-sm);
  color: var(--text-light);
  flex: 1;
}

.chapter-card__link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--card-color, var(--accent));
  margin-top: auto;
}

/* ---------- CHAPTER HERO (individual chapter pages) ---------- */
.chapter-hero {
  padding: var(--space-xl) var(--space-lg);
  background: var(--accent-light);
  border-bottom: 3px solid var(--accent);
  position: relative;
  overflow: hidden;
}

.chapter-hero::after {
  content: attr(data-emoji);
  position: absolute;
  right: 5%;
  top: 50%;
  transform: translateY(-50%);
  font-size: clamp(5rem, 12vw, 9rem);
  opacity: 0.15;
  pointer-events: none;
  line-height: 1;
}

.chapter-hero__inner {
  max-width: 700px;
}

.chapter-hero__back {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--accent);
  margin-bottom: var(--space-md);
  transition: gap 0.2s;
}

.chapter-hero__back:hover { gap: 0.2rem; }

.chapter-hero__num {
  font-family: 'Nunito', sans-serif;
  font-weight: 900;
  font-size: var(--text-sm);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

.chapter-hero__title {
  font-size: var(--text-4xl);
  margin-bottom: var(--space-sm);
}

.chapter-hero__subtitle {
  font-size: var(--text-lg);
  color: var(--text-light);
}

/* ---------- SECTION HEADERS ---------- */
.section-header {
  margin-bottom: var(--space-lg);
}

.section-header__label {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

.section-header__title {
  font-size: var(--text-3xl);
  margin-bottom: var(--space-xs);
}

.section-header__desc {
  font-size: var(--text-base);
  color: var(--text-light);
  max-width: 560px;
}

/* ---------- FUN CARDS ---------- */
.fun-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.fun-card {
  background: var(--white);
  border: 2px solid var(--gray-100);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  transition: transform 0.2s, box-shadow 0.2s;
}

.fun-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.fun-card__icon {
  font-size: 2.2rem;
  margin-bottom: var(--space-sm);
  display: block;
}

.fun-card__title {
  font-size: var(--text-lg);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  margin-bottom: var(--space-xs);
  color: var(--accent);
}

.fun-card__text {
  font-size: var(--text-sm);
  color: var(--text-light);
  line-height: 1.6;
}

/* ---------- THINK BUBBLE ---------- */
.think-bubble {
  background: linear-gradient(135deg, var(--accent-light), var(--white));
  border: 2px dashed var(--accent);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin: var(--space-lg) 0;
  position: relative;
}

.think-bubble__icon {
  font-size: 1.8rem;
  margin-bottom: var(--space-xs);
  display: block;
}

.think-bubble__title {
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-lg);
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

.think-bubble__text {
  font-size: var(--text-base);
  color: var(--text);
}

/* ---------- INTERACTIVE EXPLORER ---------- */
.explorer {
  background: var(--gray-100);
  border-radius: var(--radius-xl);
  padding: var(--space-lg);
  margin: var(--space-lg) 0;
}

.explorer__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-lg);
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.explorer__title {
  font-size: var(--text-xl);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
}

.explorer__controls {
  display: flex;
  gap: var(--space-xs);
}

.explorer__btn {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  border: 2px solid var(--accent);
  background: var(--white);
  color: var(--accent);
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s, color 0.2s;
  font-weight: bold;
}

.explorer__btn:hover {
  background: var(--accent);
  color: #fff;
}

.explorer__slide {
  display: none;
  animation: fadeSlide 0.4s ease;
}

.explorer__slide.active { display: block; }

@keyframes fadeSlide {
  from { opacity: 0; transform: translateX(15px); }
  to   { opacity: 1; transform: translateX(0); }
}

.explorer__slide-icon { font-size: 3.5rem; margin-bottom: var(--space-sm); }

.explorer__slide-title {
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-2xl);
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

.explorer__slide-text { font-size: var(--text-base); color: var(--text); line-height: 1.7; }

.explorer__dots {
  display: flex;
  gap: 8px;
  justify-content: center;
  margin-top: var(--space-md);
}

.explorer__dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--gray-200);
  cursor: pointer;
  transition: background 0.2s, transform 0.2s;
  border: none;
}

.explorer__dot.active {
  background: var(--accent);
  transform: scale(1.3);
}

/* ---------- SECRET REVEAL BUTTON ---------- */
.secret-box {
  margin: var(--space-lg) 0;
}

.secret-btn {
  width: 100%;
  background: var(--white);
  border: 2.5px dashed var(--accent);
  border-radius: var(--radius-lg);
  padding: var(--space-md) var(--space-lg);
  cursor: pointer;
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-base);
  color: var(--accent);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  transition: background 0.2s, transform 0.2s;
  text-align: left;
}

.secret-btn:hover { background: var(--accent-light); transform: scale(1.01); }

.secret-content {
  display: none;
  background: var(--accent-light);
  border: 2px solid var(--accent);
  border-top: none;
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  padding: var(--space-md) var(--space-lg);
  font-size: var(--text-base);
  animation: revealFade 0.35s ease;
}

@keyframes revealFade {
  from { opacity: 0; transform: translateY(-8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.secret-content.open { display: block; }

/* ---------- SUMMARY GRID ---------- */
.summary-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: var(--space-md);
  margin-top: var(--space-lg);
}

.summary-card {
  background: var(--white);
  border: 2px solid var(--gray-100);
  border-top: 4px solid var(--accent);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  text-align: center;
  transition: transform 0.2s, box-shadow 0.2s;
}

.summary-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }

.summary-card__icon { font-size: 2rem; margin-bottom: var(--space-xs); }

.summary-card__title {
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-sm);
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

.summary-card__text { font-size: var(--text-xs); color: var(--text-light); }

/* ---------- CHAPTER NAVIGATION FOOTER (prev/next) ---------- */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-xl) var(--space-lg);
  border-top: 2px solid var(--gray-100);
  gap: var(--space-md);
  flex-wrap: wrap;
}

.chapter-nav__btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-base);
  color: var(--accent);
  border: 2px solid var(--accent);
  padding: 0.65rem 1.4rem;
  border-radius: var(--radius-full);
  transition: background 0.2s, color 0.2s;
}

.chapter-nav__btn:hover { background: var(--accent); color: #fff; }

.chapter-nav__quiz {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 0.75rem 2rem;
  border-radius: var(--radius-full);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-base);
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  text-decoration: none;
}

.chapter-nav__quiz:hover { transform: translateY(-2px); box-shadow: var(--shadow-accent); }

/* ---------- QUIZ PAGE ---------- */
.quiz-hero {
  background: var(--off-white);
  padding: var(--space-xl) var(--space-lg);
  text-align: center;
  border-bottom: 2px solid var(--gray-100);
}

.quiz-hero__title { font-size: var(--text-4xl); margin-bottom: var(--space-xs); }
.quiz-hero__sub { font-size: var(--text-lg); color: var(--text-light); }

/* Category selector */
.quiz-categories {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
  margin: var(--space-lg) 0;
}

.quiz-cat-btn {
  padding: 0.6rem 1.2rem;
  border-radius: var(--radius-full);
  border: 2px solid var(--gray-200);
  background: var(--white);
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--text-light);
  cursor: pointer;
  transition: all 0.2s;
}

.quiz-cat-btn:hover, .quiz-cat-btn.active {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-light);
}

/* Quiz container */
.quiz-container {
  max-width: 720px;
  margin: 0 auto;
  padding: var(--space-xl) var(--space-lg);
}

/* Progress bar */
.quiz-progress {
  margin-bottom: var(--space-lg);
}

.quiz-progress__top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-xs);
}

.quiz-progress__label {
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--text-light);
}

.quiz-progress__bar {
  height: 8px;
  background: var(--gray-100);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.quiz-progress__fill {
  height: 100%;
  background: var(--accent);
  border-radius: var(--radius-full);
  transition: width 0.5s ease;
  width: 0%;
}

/* Timer */
.quiz-timer {
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-lg);
}

.quiz-timer__circle {
  position: relative;
  width: 80px;
  height: 80px;
}

.quiz-timer__svg {
  transform: rotate(-90deg);
  width: 80px;
  height: 80px;
}

.quiz-timer__track {
  fill: none;
  stroke: var(--gray-200);
  stroke-width: 6;
}

.quiz-timer__ring {
  fill: none;
  stroke: var(--accent);
  stroke-width: 6;
  stroke-linecap: round;
  stroke-dasharray: 220;
  stroke-dashoffset: 0;
  transition: stroke-dashoffset 1s linear, stroke 0.3s;
}

.quiz-timer__number {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Nunito', sans-serif;
  font-weight: 900;
  font-size: 1.4rem;
  color: var(--accent);
  transition: color 0.3s;
}

/* Question card */
.quiz-question {
  background: var(--white);
  border: 2px solid var(--gray-100);
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  margin-bottom: var(--space-lg);
  box-shadow: var(--shadow-sm);
  animation: fadeSlide 0.3s ease;
}

.quiz-question__text {
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-xl);
  color: var(--text);
  text-align: center;
  margin-bottom: var(--space-lg);
  line-height: 1.4;
}

.quiz-options {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-sm);
}

.quiz-option {
  width: 100%;
  padding: 1rem 1.2rem;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-md);
  background: var(--white);
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  font-size: var(--text-base);
  color: var(--text);
  cursor: pointer;
  text-align: center;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  min-height: 60px;
}

.quiz-option:hover:not(:disabled) {
  border-color: var(--accent);
  background: var(--accent-light);
  color: var(--accent);
  transform: scale(1.02);
}

.quiz-option.correct {
  border-color: #22c55e;
  background: #dcfce7;
  color: #15803d;
}

.quiz-option.wrong {
  border-color: #ef4444;
  background: #fee2e2;
  color: #b91c1c;
}

.quiz-option:disabled { cursor: not-allowed; }

/* Feedback */
.quiz-feedback {
  text-align: center;
  padding: var(--space-md);
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-md);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-lg);
  display: none;
}

.quiz-feedback.correct { background: #dcfce7; color: #15803d; display: block; }
.quiz-feedback.wrong   { background: #fee2e2; color: #b91c1c; display: block; }

.quiz-next {
  width: 100%;
  padding: 1rem;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius-full);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-base);
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  display: none;
}

.quiz-next.visible { display: block; }
.quiz-next:hover { transform: translateY(-2px); box-shadow: var(--shadow-accent); }

/* Result screen */
.quiz-result {
  text-align: center;
  padding: var(--space-xl);
  display: none;
}

.quiz-result.visible { display: block; animation: fadeSlide 0.5s ease; }

.quiz-result__trophy { font-size: 5rem; margin-bottom: var(--space-md); }

.quiz-result__title {
  font-size: var(--text-3xl);
  margin-bottom: var(--space-xs);
}

.quiz-result__score {
  font-family: 'Nunito', sans-serif;
  font-weight: 900;
  font-size: var(--text-4xl);
  color: var(--accent);
  margin: var(--space-md) 0;
}

.quiz-result__badge {
  display: inline-block;
  padding: 0.6rem 2rem;
  background: var(--accent-light);
  color: var(--accent);
  border-radius: var(--radius-full);
  font-family: 'Nunito', sans-serif;
  font-weight: 800;
  font-size: var(--text-lg);
  margin-bottom: var(--space-lg);
}

/* ---------- FOOTER ---------- */
footer {
  background: var(--gray-800);
  color: rgba(255,255,255,0.7);
  padding: var(--space-xl) var(--space-lg);
  text-align: center;
}

footer .footer__logo {
  font-family: 'Nunito', sans-serif;
  font-weight: 900;
  font-size: var(--text-xl);
  color: #fff;
  margin-bottom: var(--space-sm);
}

footer p { font-size: var(--text-sm); }

footer .footer__links {
  display: flex;
  justify-content: center;
  gap: var(--space-md);
  flex-wrap: wrap;
  margin: var(--space-md) 0;
}

footer .footer__links a {
  color: rgba(255,255,255,0.6);
  font-size: var(--text-sm);
  font-family: 'Nunito', sans-serif;
  font-weight: 700;
  transition: color 0.2s;
}

footer .footer__links a:hover { color: #fff; }

/* ---------- SCROLLBAR STYLING ---------- */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--gray-100); }
::-webkit-scrollbar-thumb { background: var(--gray-200); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--accent); }

/* ---------- ANIMATIONS ---------- */
/* Stagger-reveal on load */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- RESPONSIVE BREAKPOINTS ---------- */
@media (max-width: 768px) {
  .nav__links { display: none; }
  .nav__hamburger { display: flex; }

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

  .quiz-options { grid-template-columns: 1fr; }

  .chapters-grid { grid-template-columns: 1fr; }

  .chapter-hero::after { display: none; }

  .explorer__header { flex-direction: column; align-items: flex-start; }

  .chapter-nav { flex-direction: column; align-items: stretch; text-align: center; }
  .chapter-nav__btn, .chapter-nav__quiz { justify-content: center; }
}

@media (max-width: 480px) {
  .container { padding: 0 var(--space-md); }
  .fun-cards { grid-template-columns: 1fr; }
  .summary-grid { grid-template-columns: 1fr 1fr; }
}

/* ---------- REDUCED MOTION ---------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}