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

/* Design tokens */
:root {
  /* Sand palette */
  --sand-50:  #fdfcfa;
  --sand-100: #f7f5f0;
  --sand-200: #eae6dd;
  --sand-300: #d8d1c4;
  --sand-400: #b8ad9a;
  --sand-700: #5c5347;
  --sand-900: #2c2822;

  /* Ink palette */
  --ink:   #1c1917;
  --ink-2: #44403c;
  --ink-3: #78716c;

  /* Semantic */
  --hot:        #dc2626;
  --hot-bg:     #fef2f2;
  --hot-border: #fca5a5;

  /* Subject theming — overridden per page via inline :root */
  --subject-color:  var(--sand-900);
  --subject-bg:     var(--sand-100);
  --subject-border: var(--sand-300);
  --subject-text:   var(--ink-2);
}

/* Document */
html {
  scroll-behavior: smooth;
  font-size: 105%;
}

body {
  font-family: 'Lato', sans-serif;
  background: var(--sand-50);
  color: var(--ink);
  min-height: 100vh;
  overflow-x: hidden;
}

/* Dot-grid background texture */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image: radial-gradient(var(--sand-200) .5px, transparent .5px);
  background-size: 24px 24px;
  opacity: .3;
  pointer-events: none;
  z-index: 0;
}

/* Layout container */
.container {
  max-width: 80%;
  width: 80%;
  margin: 0 auto;
  padding: 0 1.25rem;
  position: relative;
  z-index: 1;
}

/* Back navigation */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  font-size: .72rem;
  color: var(--ink-3);
  text-decoration: none;
  padding: .4rem 0;
  margin-top: 1.25rem;
  font-weight: 600;
  transition: color .2s;
}
.back-link:hover { color: var(--ink) }

/* Bare page title + subtitle (outside .hero wrapper) */
.container > h1 {
  font-family: 'Newsreader', serif;
  font-size: clamp(1.25rem, 2.5vw, 1.65rem);
  font-weight: 700;
  color: var(--ink);
  line-height: 1.2;
  margin-top: 1.5rem;
  margin-bottom: .5rem;
}
.container > .subtitle {
  font-size: .8rem;
  color: var(--ink-3);
  line-height: 1.6;
  margin-bottom: 1.5rem;
  max-width: 600px;
}

/* Page hero */
.hero {
  text-align: center;
  padding: 2rem 1rem 1.5rem;
  border-bottom: 1px solid var(--sand-200);
}
.hero .badge {
  display: inline-block;
  background: var(--subject-bg);
  border: 1px solid var(--subject-border);
  border-radius: 999px;
  padding: .25rem .75rem;
  font-size: .7rem;
  color: var(--subject-color);
  margin-bottom: .75rem;
  font-weight: 700;
  letter-spacing: .05em;
  text-transform: uppercase;
}
.hero h1 {
  font-family: 'Newsreader', serif;
  font-size: clamp(1.6rem, 3.5vw, 2.2rem);
  font-weight: 700;
  color: var(--ink);
  line-height: 1.2;
}
.hero .sub {
  font-size: .82rem;
  color: var(--ink-3);
  margin: .4rem auto 0;
  max-width: 540px;
  line-height: 1.6;
}
.hero .stat-row, .hero .marks-row {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-top: 1.25rem;
  flex-wrap: wrap;
}
.hero .stat-item, .hero .marks-item {
  text-align: center;
}
.hero .stat-item .num, .hero .marks-item .num {
  font-family: 'Newsreader', serif;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--ink);
}
.hero .stat-item .lbl, .hero .marks-item .lbl {
  font-size: .62rem;
  color: var(--ink-3);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .05em;
}

/* Shared tab button (used by chapter-nav and section-nav) */
.tab {
  font-size: .82em;
  font-weight: 700;
  padding: 8px 16px;
  border: 2px solid var(--sand-300);
  border-radius: 10px;
  background: #fff;
  color: var(--sand-700);
  cursor: pointer;
  transition: all .2s;
  white-space: nowrap;
  text-decoration: none;
  display: inline-block;
  font-family: 'Lato', sans-serif;
}
.tab:hover  { border-color: var(--sand-400); color: var(--sand-900) }
.tab.active { background: var(--sand-900); color: #fff; border-color: var(--sand-900) }
.tab.read   { background: var(--sand-100); border-color: var(--sand-300); color: var(--sand-700) }
/* active always wins over read when both are present */
.tab.read.active { background: var(--sand-900); color: #fff; border-color: var(--sand-900) }

/* Monospace formula inline */
.mono { font-family: monospace; font-size: .82em }

/* Equation chip */
.eq {
  font-family: monospace;
  background: var(--sand-100);
  border-radius: 4px;
  padding: .1rem .4rem;
  font-size: .85em;
  display: inline-block;
  margin: .1rem 0;
  color: var(--ink-2);
}

/* Mobile dropdown — hidden on desktop, replaces tabs/dots on mobile */
.mobile-select {
  display: none;
  width: 100%;
  font-size: .78rem;
  font-weight: 700;
  font-family: 'Lato', sans-serif;
  padding: .5rem .75rem;
  border: 1.5px solid var(--sand-300);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath d='M3 5l3 3 3-3' fill='none' stroke='%2378716c' stroke-width='1.5' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right .75rem center;
  padding-right: 2rem;
}

/* Responsive */
@media (max-width: 640px) {
  .container { max-width: 100%; width: 100%; padding: 0 .75rem }

  /* Compact back button — pill style, touch-friendly */
  .back-link {
    font-size: .65rem;
    margin-top: .5rem;
    padding: .25rem .6rem;
    background: var(--sand-100);
    border: 1px solid var(--sand-200);
    border-radius: 999px;
    min-height: 32px;
  }

  /* Very compact hero */
  .hero {
    padding: .5rem .25rem .4rem;
  }
  .hero .badge {
    font-size: .55rem;
    padding: .1rem .45rem;
    margin-bottom: .25rem;
  }
  .hero h1 {
    font-size: .85rem;
    line-height: 1.15;
  }
  .hero .sub {
    font-size: .65rem;
    margin-top: .15rem;
    line-height: 1.4;
  }
  .hero .stat-row, .hero .marks-row {
    gap: .75rem;
    margin-top: .5rem;
  }
  .hero .stat-item .num, .hero .marks-item .num {
    font-size: .9rem;
  }
  .hero .stat-item .lbl, .hero .marks-item .lbl {
    font-size: .52rem;
  }

  /* Very compact bare page title */
  .container > h1 {
    font-size: .88rem;
    margin-top: .5rem;
    margin-bottom: .2rem;
  }
  .container > .subtitle {
    font-size: .65rem;
    margin-bottom: .75rem;
    line-height: 1.4;
  }

  /* Replace tabs/dots with dropdowns on mobile */
  .mobile-select { display: block; font-size: .72rem; }
  .chapter-tabs { display: none !important; }
  .chapter-bar .more-btn, .chapter-bar .more-dropdown { display: none !important; }
  .section-nav-inner .tab { display: none !important; }
  .section-nav .mobile-select { display: block; }

  /* Compact footer */
  .site-footer {
    margin-top: 2rem;
    padding: 1rem 0 1.5rem;
    font-size: .65rem;
  }
}

/* Site footer */
.site-footer {
  margin-top: 4rem;
  padding: 1.5rem 0 2rem;
  border-top: 1px solid var(--sand-200);
  text-align: center;
  font-size: .72rem;
  color: var(--ink-3);
  line-height: 1.8;
}
.site-footer a { color: var(--ink-3); text-decoration: underline; text-underline-offset: 2px }
.site-footer a:hover { color: var(--ink) }