/* ==========================================================================
   Lerncampus BW - Stylesheet (Vibrant Educational Theme)
   Design: Modern, Premium, Friendly & Structured (Klett/Cornelsen-Inspired)
   ========================================================================== */

/* --- Custom Properties & Theme System --- */
:root {
  /* Colors - Light Theme (Default) */
  --bg-primary: #f9f9f6;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f3f0;
  --text-primary: #2d2d2d;
  --text-secondary: #424e45;
  --text-muted: #8b988f;
  --border-color: #e2e8e3;
  --focus-ring: rgba(26, 77, 51, 0.15);

  /* Primary Brand (Deep Forest Green from Mathe Cover) */
  --color-primary: #1a4d33;
  --color-primary-hover: #113622;
  --color-primary-light: #f1f6f2;

  /* Theme colors for subjects matching cover colors */
  --color-deutsch: #f3a61e;       /* Bright Cover Yellow */
  --color-deutsch-dark: #cc840c;
  --color-deutsch-light: #fef5e7;
  --color-deutsch-bg: #fffbf5;
  
  --color-mathe: #27522d;         /* Deep Forest Green */
  --color-mathe-dark: #1b3d20;
  --color-mathe-light: #e5ede7;
  --color-mathe-bg: #f6faf7;
  
  --color-englisch: #1b4f72;      /* Royal blue */
  --color-englisch-dark: #123750;
  --color-englisch-light: #e8f0fe;
  --color-englisch-bg: #f4f8fd;
  
  --color-methodik: #7c3aed;      /* Inspirational purple */
  --color-methodik-dark: #5b21b6;
  --color-methodik-light: #f3e8ff;
  --color-methodik-bg: #faf5ff;

  /* Layout & Spacing */
  --container-max-width: 1200px;
  --transition-smooth: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  --transition-fast: all 0.15s ease-in-out;
  
  /* Fonts */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-display: 'Outfit', sans-serif;
}

/* Dark Theme overrides */
body.dark-theme {
  --bg-primary: #0e1410;
  --bg-secondary: #18221b;
  --bg-tertiary: #222f26;
  --text-primary: #f2f7f4;
  --text-secondary: #c2d1c6;
  --text-muted: #728477;
  --border-color: #2c3a30;
  --focus-ring: rgba(39, 82, 45, 0.4);

  --color-primary: #4e8d58;
  --color-primary-hover: #67a671;
  --color-primary-light: rgba(78, 141, 88, 0.1);

  --color-deutsch-bg: rgba(243, 166, 30, 0.1);
  --color-mathe-bg: rgba(39, 82, 45, 0.1);
  --color-englisch-bg: rgba(27, 79, 114, 0.1);
  --color-methodik-bg: rgba(124, 58, 237, 0.1);
}

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

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
  position: relative;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* Decorative modern background blobs */
.decorative-blob {
  position: absolute;
  width: 500px;
  height: 500px;
  border-radius: 50%;
  filter: blur(120px);
  z-index: -1;
  opacity: 0.35;
  pointer-events: none;
  transition: var(--transition-smooth);
}
.blob-1 {
  top: -100px;
  right: -100px;
  background-color: var(--color-primary-light);
}
.blob-2 {
  top: 800px;
  left: -200px;
  background-color: var(--color-mathe-light);
}
body.dark-theme .decorative-blob {
  opacity: 0.15;
}

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

p {
  color: var(--text-secondary);
}

a {
  color: inherit;
  text-decoration: none;
  transition: var(--transition-fast);
}

/* Utilities */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: 24px;
  padding-right: 24px;
}

.weight-bold { font-weight: 800; }
.text-highlight {
  color: var(--color-primary);
  position: relative;
}

/* --- Buttons & CTAs --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 30px;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 30px; /* Modern rounded buttons */
  cursor: pointer;
  transition: var(--transition-smooth);
  font-family: var(--font-display);
}

.btn-primary {
  background-color: var(--color-primary);
  color: #ffffff;
  border: 2px solid var(--color-primary);
  box-shadow: 0 4px 14px rgba(14, 116, 144, 0.2);
}

.btn-primary:hover {
  background-color: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(14, 116, 144, 0.3);
}

.btn-primary .arrow-icon {
  width: 18px;
  height: 18px;
  margin-left: 8px;
  transition: transform 0.2s ease;
}

.btn-primary:hover .arrow-icon {
  transform: translateX(4px);
}

.btn-secondary {
  background-color: var(--bg-secondary);
  color: var(--color-primary);
  border: 2px solid var(--color-primary);
}

.btn-secondary:hover {
  background-color: var(--color-primary-light);
  transform: translateY(-2px);
}

/* --- Header & Navigation --- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

body.dark-theme .site-header {
  background-color: rgba(15, 23, 42, 0.9);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 84px;
}

.logo-container {
  display: flex;
  align-items: center;
  gap: 12px;
}

.site-logo {
  width: 44px;
  height: 44px;
}

.logo-text {
  font-family: var(--font-display);
  font-size: 1.3rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.main-navigation ul {
  display: flex;
  list-style: none;
  gap: 32px;
}

.nav-link {
  font-family: var(--font-display);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-secondary);
  position: relative;
  padding: 8px 0;
}

.nav-link:hover {
  color: var(--color-primary);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 3px;
  border-radius: 2px;
  background-color: var(--color-primary);
  transition: var(--transition-fast);
}

.nav-link:hover::after {
  width: 100%;
}

/* Theme Toggle Button */
.theme-toggle {
  background: none;
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  width: 40px;
  height: 40px;
  border-radius: 50%; /* Modern circle toggle */
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition-fast);
}

.theme-toggle:hover {
  background-color: var(--bg-tertiary);
  border-color: var(--color-primary);
}

.theme-toggle .sun-icon {
  display: none;
  width: 20px;
  height: 20px;
}

.theme-toggle .moon-icon {
  display: block;
  width: 20px;
  height: 20px;
}

body.dark-theme .theme-toggle .sun-icon {
  display: block;
}

body.dark-theme .theme-toggle .moon-icon {
  display: none;
}

/* Mobile Nav Toggle */
.mobile-nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 24px;
  height: 18px;
  background: none;
  border: none;
  cursor: pointer;
  z-index: 110;
}

.hamburger-bar {
  width: 100%;
  height: 2px;
  background-color: var(--text-primary);
  transition: var(--transition-smooth);
}

/* Mobile Nav Menu Drawer */
.mobile-nav-menu {
  position: fixed;
  top: 84px;
  left: 0;
  width: 100%;
  height: calc(100vh - 84px);
  background-color: var(--bg-primary);
  z-index: 99;
  display: flex;
  flex-direction: column;
  padding: 40px 24px;
  border-top: 1px solid var(--border-color);
  transform: translateY(-100%);
  opacity: 0;
  pointer-events: none;
  transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.3s ease;
}

.mobile-nav-menu.is-active {
  transform: translateY(0);
  opacity: 1;
  pointer-events: all;
}

.mobile-navigation ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.mobile-nav-link {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-primary);
}

/* --- Hero Section --- */
.hero-section {
  padding-top: 80px;
  padding-bottom: 80px;
}

.hero-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}

.hero-tagline {
  font-family: var(--font-display);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--color-primary);
  background-color: var(--color-primary-light);
  padding: 6px 16px;
  border-radius: 20px;
  margin-bottom: 24px;
}

.hero-title {
  font-size: 3.5rem;
  font-weight: 800;
  max-width: 850px;
  margin-bottom: 24px;
  line-height: 1.2;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 650px;
  margin-bottom: 40px;
  font-weight: 400;
}

.hero-ctas {
  display: flex;
  gap: 16px;
  margin-bottom: 60px;
}

/* Interactive Mockup styling in Hero */
.hero-visual {
  width: 100%;
  max-width: 850px;
  background-color: var(--bg-secondary);
  border-radius: 16px;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.05);
  overflow: hidden;
  border: 1px solid var(--border-color);
  transition: var(--transition-smooth);
}

body.dark-theme .hero-visual {
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
}

.hero-visual:hover {
  transform: translateY(-4px);
  box-shadow: 0 15px 50px rgba(0, 0, 0, 0.08);
}

.mockup-header-tabs {
  background-color: var(--bg-tertiary);
  display: flex;
  padding: 12px 24px;
  gap: 16px;
  border-bottom: 1px solid var(--border-color);
}

.tab-indicator {
  font-family: var(--font-display);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 4px 12px;
  border-radius: 12px;
  color: var(--text-secondary);
  background-color: var(--bg-secondary);
}

.deutsch-tab { border-left: 3px solid var(--color-deutsch); }
.mathe-tab { border-left: 3px solid var(--color-mathe); }
.englisch-tab { border-left: 3px solid var(--color-englisch); }
.methodik-tab { border-left: 3px solid var(--color-methodik); }

.visual-card {
  padding: 32px;
  background-color: var(--bg-secondary);
}

.visual-card-inner {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.badge {
  align-self: flex-start;
  font-family: var(--font-display);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 4px 12px;
  border-radius: 20px;
}

.badge-primary {
  background-color: var(--color-primary-light);
  color: var(--color-primary);
}

.mockup-page {
  background: var(--bg-primary);
  border-radius: 12px;
  padding: 24px;
}

.mockup-grid {
  display: grid;
  grid-template-columns: 0.8fr 1.2fr;
  gap: 32px;
  align-items: center;
}

.mockup-illustration {
  height: 180px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--bg-secondary);
  border-radius: 8px;
  border: 1px solid var(--border-color);
}

.mockup-text-area {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.mockup-line {
  background-color: var(--border-color);
  height: 8px;
  border-radius: 4px;
}

.mockup-line.accent-line {
  height: 14px;
  border-radius: 6px;
}

.mockup-btn-placeholder {
  align-self: flex-start;
  margin-top: 12px;
  font-family: var(--font-display);
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
  padding: 6px 16px;
  border-radius: 20px;
  background-color: var(--bg-secondary);
}

/* --- Section Headers --- */
.section-header {
  text-align: center;
  max-width: 700px;
  margin: 0 auto 60px auto;
}

.section-title {
  font-size: 2.5rem;
  margin-bottom: 16px;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
}

/* --- Portfolio / Dynamic Booklet Gallery --- */
.portfolio-section {
  padding: 100px 0;
}

.booklet-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 36px;
  margin-top: 40px;
}

@media (min-width: 1024px) {
  .booklet-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.booklet-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 24px;
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.02);
  transition: var(--transition-smooth);
  position: relative;
  overflow: hidden;
}

@media (min-width: 480px) {
  .booklet-card {
    flex-direction: row;
    align-items: stretch;
  }
}

.booklet-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.05);
}

/* Color theme frames for the cards - like the covers! */
.booklet-card.theme-deutsch {
  border-top: 6px solid var(--color-deutsch);
  background-color: var(--color-deutsch-bg);
}
body.dark-theme .booklet-card.theme-deutsch {
  background-color: var(--bg-secondary);
  border-color: rgba(243, 166, 30, 0.3);
}

.booklet-card.theme-mathe {
  border-top: 6px solid var(--color-mathe);
  background-color: var(--color-mathe-bg);
}
body.dark-theme .booklet-card.theme-mathe {
  background-color: var(--bg-secondary);
  border-color: rgba(39, 82, 45, 0.3);
}

.booklet-card.theme-englisch {
  border-top: 6px solid var(--color-englisch);
  background-color: var(--color-englisch-bg);
}
body.dark-theme .booklet-card.theme-englisch {
  background-color: var(--bg-secondary);
  border-color: rgba(27, 79, 114, 0.3);
}

.booklet-card.theme-methodik {
  border-top: 6px solid var(--color-methodik);
  background-color: var(--color-methodik-bg);
}
body.dark-theme .booklet-card.theme-methodik {
  background-color: var(--bg-secondary);
  border-color: rgba(124, 58, 237, 0.3);
}

.booklet-cover-side {
  flex: 0 0 auto;
  display: flex;
  justify-content: center;
  align-items: center;
  min-width: 160px;
}

.booklet-info-side {
  flex: 1 1 auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
  justify-content: space-between;
}

/* Subject Badges */
.booklet-badge {
  align-self: flex-start;
  font-family: var(--font-display);
  font-size: 0.7rem;
  font-weight: 800;
  text-transform: uppercase;
  padding: 4px 12px;
  border-radius: 12px;
  letter-spacing: 0.05em;
}

.theme-deutsch .booklet-badge { background-color: var(--color-deutsch-light); color: var(--color-deutsch-dark); }
.theme-mathe .booklet-badge { background-color: var(--color-mathe-light); color: var(--color-mathe); }
.theme-englisch .booklet-badge { background-color: var(--color-englisch-light); color: var(--color-englisch); }
.theme-methodik .booklet-badge { background-color: var(--color-methodik-light); color: var(--color-methodik); }

/* Booklet Title & Details */
.booklet-title {
  font-size: 1.4rem;
  font-weight: 800;
  line-height: 1.2;
  color: var(--text-primary);
  margin-bottom: 2px;
}

.booklet-subtitle {
  font-family: var(--font-display);
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 2px;
}
.theme-deutsch .booklet-subtitle { color: var(--color-deutsch-dark); }
.theme-mathe .booklet-subtitle { color: var(--color-mathe); }
.theme-englisch .booklet-subtitle { color: var(--color-englisch); }
.theme-methodik .booklet-subtitle { color: var(--color-methodik); }

.booklet-details {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
}

/* Bullet list */
.booklet-features {
  list-style: none;
  margin-bottom: 12px;
}

.booklet-features li {
  position: relative;
  padding-left: 20px;
  margin-bottom: 6px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.booklet-features li::before {
  content: '✓';
  position: absolute;
  left: 0;
  font-weight: bold;
}
.theme-deutsch .booklet-features li::before { color: var(--color-deutsch); }
.theme-mathe .booklet-features li::before { color: var(--color-mathe); }
.theme-englisch .booklet-features li::before { color: var(--color-englisch); }
.theme-methodik .booklet-features li::before { color: var(--color-methodik); }

/* Buy button */
.btn-buy {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 22px;
  font-size: 0.85rem;
  font-weight: 700;
  border-radius: 20px;
  cursor: pointer;
  font-family: var(--font-display);
  border: 1px solid transparent;
  gap: 8px;
  align-self: flex-start;
  transition: var(--transition-smooth);
}

.theme-deutsch .btn-buy {
  background-color: var(--color-deutsch);
  color: #ffffff;
}
.theme-deutsch .btn-buy:hover {
  background-color: var(--color-deutsch-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(243, 166, 30, 0.2);
}

.theme-mathe .btn-buy {
  background-color: var(--color-mathe);
  color: #ffffff;
}
.theme-mathe .btn-buy:hover {
  background-color: var(--color-mathe-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(39, 82, 45, 0.2);
}

.theme-englisch .btn-buy {
  background-color: var(--color-englisch);
  color: #ffffff;
}
.theme-englisch .btn-buy:hover {
  background-color: var(--color-englisch-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(27, 79, 114, 0.2);
}

.theme-methodik .btn-buy {
  background-color: var(--color-methodik);
  color: #ffffff;
}
.theme-methodik .btn-buy:hover {
  background-color: var(--color-methodik-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(124, 58, 237, 0.2);
}

.btn-buy .amazon-icon {
  width: 14px;
  height: 14px;
  fill: currentColor;
}

/* 3D Cover Mockup */
.book-cover-container {
  perspective: 800px;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding-top: 32px;
}

.book-cover-3d {
  width: 140px;
  height: 181px;
  position: relative;
  transform: rotateY(-10deg) rotateX(3deg);
  transform-style: preserve-3d;
  box-shadow: 4px 6px 15px rgba(0, 0, 0, 0.12), 
              1px 1px 2px rgba(0, 0, 0, 0.04);
  transition: transform 0.4s ease, box-shadow 0.4s ease;
  border-radius: 2px 8px 8px 2px;
  background-color: #f1f3f0;
}

.booklet-card:hover .book-cover-3d {
  transform: rotateY(-2deg) rotateX(1deg) translateY(-4px);
  box-shadow: 8px 12px 25px rgba(0, 0, 0, 0.18), 
              1px 1px 4px rgba(0, 0, 0, 0.06);
}

.book-cover-3d img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 2px 8px 8px 2px;
  display: block;
}

/* Spine effect for 3D look */
.book-cover-3d::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 6px;
  height: 100%;
  background: linear-gradient(to right, rgba(0, 0, 0, 0.15) 0%, rgba(255, 255, 255, 0.12) 50%, rgba(0, 0, 0, 0.08) 100%);
  border-radius: 2px 0 0 2px;
  z-index: 2;
}

/* CSS-based book cover fallback */
.css-book-cover {
  width: 140px;
  height: 181px;
  background-color: var(--color-primary);
  border-radius: 2px 8px 8px 2px;
  padding: 8px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  position: relative;
  overflow: hidden;
  box-shadow: 4px 6px 15px rgba(0, 0, 0, 0.12);
  transition: transform 0.4s ease, box-shadow 0.4s ease;
  transform: rotateY(-10deg) rotateX(3deg);
  transform-style: preserve-3d;
}

.booklet-card:hover .css-book-cover {
  transform: rotateY(-2deg) rotateX(1deg) translateY(-4px);
  box-shadow: 8px 12px 25px rgba(0, 0, 0, 0.18);
}

.css-book-cover::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 6px;
  height: 100%;
  background: linear-gradient(to right, rgba(0, 0, 0, 0.15) 0%, rgba(255, 255, 255, 0.12) 50%, rgba(0, 0, 0, 0.08) 100%);
  border-radius: 2px 0 0 2px;
  z-index: 2;
}

/* Cover White Wavy Header Shape */
.css-book-cover .cover-header {
  background: #ffffff;
  border-radius: 6px 6px 10px 10px / 5px 5px 8px 8px;
  padding: 4px;
  text-align: center;
  color: #1c241e;
  border: 1px solid rgba(0, 0, 0, 0.1);
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}

.css-book-cover .cover-title {
  font-family: var(--font-display);
  font-size: 0.8rem;
  font-weight: 800;
  margin-bottom: 1px;
  color: #1c241e;
  line-height: 1.1;
}

.css-book-cover .cover-subtitle {
  font-size: 0.6rem;
  font-weight: 700;
  line-height: 1.1;
}
.theme-deutsch .css-book-cover .cover-subtitle { color: var(--color-deutsch-dark); }
.theme-mathe .css-book-cover .cover-subtitle { color: var(--color-mathe); }
.theme-englisch .css-book-cover .cover-subtitle { color: var(--color-englisch); }
.theme-methodik .css-book-cover .cover-subtitle { color: var(--color-methodik); }

.css-book-cover .cover-details {
  font-size: 0.5rem;
  font-weight: 600;
  color: var(--text-muted);
  line-height: 1;
  margin-top: 1px;
}

/* Illustration in the middle */
.css-book-cover .cover-illustration {
  flex-grow: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 5px 0;
  background: rgba(255, 255, 255, 0.85);
  border-radius: 4px;
  padding: 4px;
}

.css-book-cover .cover-illustration svg {
  width: 32px;
  height: 32px;
}

/* Cover bottom area */
.css-book-cover .cover-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 2px;
}

.css-book-cover .cover-brand {
  font-size: 0.5rem;
  font-weight: 700;
  color: #ffffff;
  font-family: var(--font-display);
  opacity: 0.95;
}

.css-book-cover .cover-backpack-badge {
  width: 16px;
  height: 16px;
  background-color: #c9252c;
  border-radius: 3px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 0.5px solid rgba(255, 255, 255, 0.8);
}

.css-book-cover .cover-backpack-badge svg {
  width: 10px;
  height: 10px;
  fill: #ffffff;
}

/* Cover specific theme adjustments */
.theme-deutsch .css-book-cover { background-color: var(--color-deutsch); }
.theme-mathe .css-book-cover { background-color: var(--color-mathe); }
.theme-englisch .css-book-cover { background-color: var(--color-englisch); }
.theme-methodik .css-book-cover { background-color: var(--color-methodik); }

/* --- Concept / Authors Section --- */
.concept-section {
  padding: 100px 0;
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  border-bottom: 1px solid var(--border-color);
}

body.dark-theme .concept-section {
  background-color: #111827;
}

.concept-container {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 60px;
  align-items: center;
}

.concept-label {
  font-family: var(--font-display);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-primary);
  margin-bottom: 16px;
  display: block;
}

.concept-title {
  font-size: 2.5rem;
  margin-bottom: 24px;
}

.concept-lead {
  font-size: 1.2rem;
  font-weight: 500;
  color: var(--text-primary);
  margin-bottom: 20px;
}

.concept-text {
  display: flex;
  flex-direction: column;
  gap: 16px;
  margin-bottom: 32px;
}

.concept-features {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.feature-item {
  display: flex;
  gap: 16px;
  font-size: 0.95rem;
}

.feature-indicator {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  margin-top: 6px;
  flex-shrink: 0;
}

/* Blueprint design visualization */
.blueprint {
  border: 1px solid var(--border-color);
  background-color: var(--bg-primary);
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 4px 30px rgba(0, 0, 0, 0.02);
}

.blueprint-header {
  background-color: var(--bg-tertiary);
  border-bottom: 1px solid var(--border-color);
  padding: 14px 20px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.blueprint-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.blueprint-label {
  font-family: var(--font-display);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-left: 8px;
}

.blueprint-body {
  padding: 28px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.bp-grid-box {
  border: 2px dashed var(--border-color);
  padding: 20px;
  position: relative;
  border-radius: 8px;
}

.bp-grid-box::before {
  content: attr(data-label);
  position: absolute;
  top: -9px;
  left: 14px;
  background-color: var(--bg-primary);
  padding: 0 8px;
  font-size: 0.65rem;
  color: var(--text-muted);
  font-family: var(--font-display);
  font-weight: 700;
  text-transform: uppercase;
}

.bp-line {
  height: 8px;
  background-color: var(--bg-tertiary);
  border-radius: 4px;
  width: 100%;
}

.bp-thick {
  height: 12px;
  width: 70%;
  margin-bottom: 8px;
}

.bp-short {
  width: 45%;
}

/* --- FAQ Section --- */
.faq-section {
  padding: 100px 0;
}

.faq-list {
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  border: 1px solid var(--border-color);
  border-radius: 12px;
  margin-bottom: 20px;
  overflow: hidden;
  background-color: var(--bg-secondary);
  transition: var(--transition-fast);
}

.faq-item[open] {
  border-color: var(--color-primary);
  box-shadow: 0 4px 20px rgba(14, 116, 144, 0.05);
}

.faq-question {
  padding: 24px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.15rem;
  cursor: pointer;
  user-select: none;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::after {
  content: '+';
  font-size: 1.6rem;
  font-weight: 300;
  color: var(--color-primary);
  transition: transform 0.2s ease;
}

.faq-item[open] .faq-question::after {
  transform: rotate(45deg);
}

.faq-answer {
  padding: 0 24px 24px 24px;
  color: var(--text-secondary);
  border-top: 1px solid transparent;
  font-size: 0.95rem;
}

.faq-item[open] .faq-answer {
  border-top-color: var(--border-color);
}

/* --- Contact Section --- */
.contact-section {
  padding: 100px 0;
}

.contact-container {
  display: flex;
  justify-content: center;
}

.contact-card {
  width: 100%;
  max-width: 850px;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: 60px 40px;
  border-radius: 20px;
  text-align: center;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.03);
}

.contact-title {
  font-size: 2.25rem;
  margin-bottom: 16px;
}

.contact-subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 550px;
  margin: 0 auto 36px auto;
}

.contact-actions {
  display: flex;
  justify-content: center;
  gap: 16px;
}

/* --- Footer Section --- */
.site-footer {
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 80px 0 40px 0;
}

body.dark-theme .site-footer {
  background-color: #0f172a;
}

.footer-container {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 60px;
  margin-bottom: 60px;
}

.footer-brand {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.footer-description {
  font-size: 0.95rem;
  max-width: 320px;
}

.footer-nav-title {
  font-family: var(--font-display);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 24px;
  font-weight: 700;
}

.footer-nav ul,
.footer-legal ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.footer-nav a,
.footer-legal a {
  font-size: 0.95rem;
  color: var(--text-secondary);
}

.footer-nav a:hover,
.footer-legal a:hover {
  color: var(--color-primary);
}

.footer-bottom {
  border-top: 1px solid var(--border-color);
  padding-top: 40px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.copyright {
  font-size: 0.85rem;
  color: var(--text-muted);
  width: 100%;
}

/* --- Entry Animations --- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-fade-in-up {
  animation: fadeInUp 0.8s cubic-bezier(0.16, 1, 0.3, 1) forwards;
  opacity: 0;
}

.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }

/* --- Scroll Animation System (controlled by main.js) --- */
.animate-scroll-base {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1), transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.animate-active {
  opacity: 1;
  transform: translateY(0);
}

/* --- Responsive Adjustments (Mobile-First) --- */
@media (max-width: 1024px) {
  .concept-container {
    grid-template-columns: 1fr;
    gap: 40px;
  }
  
  .concept-visual {
    order: -1;
    max-width: 500px;
    margin: 0 auto;
    width: 100%;
  }
}

@media (max-width: 768px) {
  .hero-title {
    font-size: 2.5rem;
  }
  
  .hero-subtitle {
    font-size: 1.1rem;
  }
  
  .hero-ctas {
    flex-direction: column;
    width: 100%;
    max-width: 320px;
  }
  
  .portfolio-grid {
    grid-template-columns: 1fr;
    gap: 24px;
  }
  
  .footer-container {
    grid-template-columns: 1fr;
    gap: 40px;
  }
  
  .mobile-nav-toggle {
    display: flex;
  }
  
  .main-navigation {
    display: none;
  }
  
  .mockup-grid {
    grid-template-columns: 1fr;
    gap: 24px;
  }
  
  /* Hamburger to Close morph */
  .mobile-nav-toggle.is-active .hamburger-bar:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
  }
  
  .mobile-nav-toggle.is-active .hamburger-bar:nth-child(2) {
    opacity: 0;
  }
  
  .mobile-nav-toggle.is-active .hamburger-bar:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
  }
  
  .contact-card {
    padding: 40px 20px;
  }
  
  .contact-actions {
    flex-direction: column;
    align-items: center;
  }
  
  .contact-actions .btn {
    width: 100%;
    max-width: 300px;
  }
}

/* ==========================================================================
   Interactive Tab Box (Hero Section)
   ========================================================================== */
.interactive-tab-box {
  margin-top: 48px;
  width: 100%;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
  background-color: var(--bg-secondary);
  border-radius: 16px;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.08);
  overflow: hidden;
  border: 1px solid var(--border-color);
}

.tab-navigation {
  display: flex;
  background-color: var(--bg-tertiary);
  border-bottom: 1px solid var(--border-color);
  overflow-x: auto;
  scrollbar-width: none;
}
.tab-navigation::-webkit-scrollbar {
  display: none;
}

.tab-btn {
  flex: 1;
  min-width: 120px;
  padding: 16px 20px;
  background: transparent;
  border: none;
  font-family: var(--font-primary);
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.3s ease;
  position: relative;
  text-align: center;
}

.tab-btn:hover {
  background-color: rgba(0, 0, 0, 0.02);
  color: var(--color-primary);
}

.tab-btn.active {
  color: var(--color-primary);
  background-color: var(--bg-secondary);
}

.tab-btn.active::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  width: 100%;
  height: 3px;
  background-color: var(--color-primary);
  border-radius: 3px 3px 0 0;
}

.tab-content-container {
  padding: 32px;
}

.tab-panel {
  display: none;
  animation: fadeIn 0.4s ease forwards;
}

.tab-panel.active {
  display: block;
}

.tab-panel-inner {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

@media (min-width: 600px) {
  .tab-panel-inner {
    flex-direction: row;
    align-items: center;
    gap: 32px;
  }
}

.tab-mockup-placeholder {
  flex: 0 0 140px;
  height: 180px;
  border-radius: 8px;
  display: flex;
  justify-content: center;
  align-items: center;
  box-shadow: 4px 6px 15px rgba(0, 0, 0, 0.1);
  color: white;
  font-family: var(--font-display);
  font-size: 2.5rem;
  font-weight: 800;
  position: relative;
}
.tab-mockup-placeholder::after {
  content: '';
  position: absolute;
  top: 0; left: 0; bottom: 0; width: 8px;
  background: rgba(0,0,0,0.1);
  border-radius: 8px 0 0 8px;
}

.mockup-deutsch { background-color: var(--color-deutsch); }
.mockup-mathe { background-color: var(--color-mathe); }
.mockup-englisch { background-color: var(--color-englisch); }
.mockup-methodik { background-color: var(--color-methodik); }

.tab-text-content {
  flex: 1;
  text-align: left;
}

.tab-text-content h3 {
  font-size: 1.4rem;
  color: var(--color-primary);
  margin-bottom: 12px;
  line-height: 1.3;
}

.tab-text-content p {
  color: var(--text-primary);
  font-size: 1rem;
  line-height: 1.6;
  margin-bottom: 24px;
}

.btn-sm {
  padding: 10px 20px;
  font-size: 0.95rem;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}