/* ============================================================
   UP Board Physics — token system
   ink:      #14181F  (primary bg, text on paper)
   navy:     #1B2A41  (section bg)
   paper:    #FAF7F2  (card bg)
   marigold: #E8A33D  (accent — chalk/marigold)
   teal:     #4FA69C  (secondary accent — circuit line)
   muted:    #8B96A8  (captions on navy)
   ============================================================ */

:root {
  --ink: #14181F;
  --navy: #1B2A41;
  --navy-2: #223452;
  --paper: #FAF7F2;
  --marigold: #E8A33D;
  --teal: #4FA69C;
  --muted: #8B96A8;
  --border: rgba(250, 247, 242, 0.12);
  --radius: 2px;
  --font-display: 'IBM Plex Serif', Georgia, serif;
  --font-body: 'IBM Plex Sans', 'Noto Sans Devanagari', system-ui, sans-serif;
  --font-mono: 'IBM Plex Mono', ui-monospace, monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--navy);
  color: var(--paper);
  font-family: var(--font-body);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

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

/* ---------- layout shell ---------- */
.wrap {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- top bar ---------- */
.topbar {
  border-bottom: 1px solid var(--border);
  padding: 18px 0;
  position: sticky;
  top: 0;
  background: rgba(27, 42, 65, 0.92);
  backdrop-filter: blur(6px);
  z-index: 10;
}
.topbar .wrap { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 12px; }
.brand {
  font-family: var(--font-mono);
  font-size: 14px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-decoration: none;
  color: var(--paper);
  display: flex;
  align-items: baseline;
  gap: 8px;
}
.brand .dot { color: var(--marigold); }
.nav-links { display: flex; gap: 18px; font-size: 14px; align-items: center; flex-wrap: wrap; }
.nav-links a { text-decoration: none; color: var(--muted); transition: color .15s; }
.nav-links a:hover, .nav-links a.active { color: var(--paper); }

/* language toggle (site UI text) — now labeled English Medium / हिंदी माध्यम */
.lang-toggle {
  display: flex;
  border: 1px solid var(--teal);
  border-radius: var(--radius);
  overflow: hidden;
  font-family: var(--font-body);
  font-size: 12px;
}
.lang-toggle button {
  background: transparent;
  border: none;
  color: var(--muted);
  padding: 6px 12px;
  cursor: pointer;
  font-family: inherit;
  white-space: nowrap;
  font-size: inherit;
}
.lang-toggle button.active { background: var(--marigold); color: var(--ink); font-weight: 600; }

/* subject switcher */
.subject-links { display: flex; gap: 4px; font-size: 14px; }
.subject-links a {
  text-decoration: none;
  color: var(--muted);
  padding: 6px 10px;
  border-radius: var(--radius);
}
.subject-links a:hover { color: var(--paper); }
.subject-links a.active { color: var(--ink); background: var(--marigold); font-weight: 600; }

/* show/hide video by selected language */
body[data-lang="en"] [data-video-lang="hi"] { display: none; }
body[data-lang="hi"] [data-video-lang="en"] { display: none; }

/* ---------- hero ---------- */
.hero {
  padding: 72px 0 56px;
  position: relative;
  overflow: hidden;
}
.hero-eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--teal);
  margin: 0 0 14px;
}
.hero h1 {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: clamp(32px, 5vw, 54px);
  line-height: 1.08;
  margin: 0 0 18px;
  max-width: 15ch;
}
.hero h1 em { font-style: italic; color: var(--marigold); }
.hero p.lead {
  font-size: 17px;
  color: var(--muted);
  max-width: 52ch;
  margin: 0 0 28px;
}
.hero-stats {
  display: flex;
  gap: 32px;
  flex-wrap: wrap;
  margin-top: 8px;
}
.hero-stats div { border-left: 2px solid var(--marigold); padding-left: 12px; }
.hero-stats .num { font-family: var(--font-mono); font-size: 22px; color: var(--paper); display: block; }
.hero-stats .label { font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: .04em; }

/* circuit line SVG sits behind hero text */
.circuit-bg {
  position: absolute;
  right: -60px;
  top: 0;
  width: 480px;
  max-width: 60%;
  opacity: 0.35;
  pointer-events: none;
}

/* ---------- section headers (exam-paper style) ---------- */
.paper-section { padding: 8px 0 48px; }
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  border-bottom: 2px solid var(--border);
  padding-bottom: 14px;
  margin-bottom: 28px;
  flex-wrap: wrap;
  gap: 8px;
}
.section-head .label {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--marigold);
}
.section-head h2 {
  font-family: var(--font-display);
  font-size: 26px;
  margin: 4px 0 0;
  font-weight: 500;
}
.section-head .marks {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--muted);
  border: 1px solid var(--border);
  padding: 4px 10px;
  border-radius: var(--radius);
  white-space: nowrap;
}

/* ---------- unit grid / cards ---------- */
.unit-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}
.unit-card {
  background: var(--paper);
  color: var(--ink);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  position: relative;
  border: 1px solid transparent;
  transition: transform .18s ease, box-shadow .18s ease;
}
.unit-card:hover { transform: translateY(-3px); box-shadow: 0 12px 28px rgba(0,0,0,0.28); }
.unit-card .unit-index {
  position: absolute;
  top: 14px;
  left: 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  background: var(--ink);
  color: var(--paper);
  padding: 3px 8px;
  border-radius: var(--radius);
  z-index: 2;
}
.unit-card .thumb {
  aspect-ratio: 16/9;
  background: #0e131a;
  position: relative;
}
.unit-card .thumb iframe {
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}
.unit-card .thumb .placeholder {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 12px;
  text-align: center;
  padding: 12px;
}
.unit-card .body { padding: 16px 18px 18px; flex: 1; display: flex; flex-direction: column; }
.unit-card h3 {
  font-family: var(--font-display);
  font-size: 18px;
  margin: 0 0 6px;
  font-weight: 600;
}
.unit-card .topics {
  font-size: 13px;
  color: #4b5563;
  margin: 0 0 14px;
  flex: 1;
}
.unit-card .meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 12px;
  color: #6b7280;
  border-top: 1px dashed #d8d2c5;
  padding-top: 10px;
}
.unit-card .meta .weight { color: var(--marigold); font-weight: 600; }
.unit-card.high-yield .weight::after { content: " · high-yield"; color: #b8811f; }

/* ---------- ad slot ---------- */
.ad-slot {
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 18px;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
  margin: 40px 0;
  min-height: 90px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ---------- footer ---------- */
footer {
  border-top: 1px solid var(--border);
  padding: 32px 0 48px;
  font-size: 13px;
  color: var(--muted);
}
footer .wrap { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 12px; }
footer a { text-decoration: none; }
footer a:hover { color: var(--paper); }

/* ---------- simple pages (about/privacy/contact) ---------- */
.doc { padding: 56px 0; max-width: 720px; margin: 0 auto; }
.doc h1 { font-family: var(--font-display); font-size: 34px; margin-bottom: 6px; }
.doc .updated { color: var(--muted); font-size: 13px; font-family: var(--font-mono); margin-bottom: 32px; }
.doc h2 { font-family: var(--font-display); font-size: 20px; margin-top: 32px; }
.doc p, .doc li { color: #cfd6e2; font-size: 15px; line-height: 1.7; }

/* ---------- papers (paid) page ---------- */
.paper-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 20px;
}
.paper-item {
  background: var(--paper);
  color: var(--ink);
  border-radius: var(--radius);
  padding: 22px 20px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.paper-item .year {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--teal);
}
.paper-item h3 { font-family: var(--font-display); font-size: 19px; margin: 0; }
.paper-item .desc { font-size: 13px; color: #4b5563; flex: 1; }
.paper-item .price-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px dashed #d8d2c5;
  padding-top: 12px;
}
.paper-item .price { font-family: var(--font-mono); font-size: 16px; font-weight: 600; }
.buy-btn {
  background: var(--ink);
  color: var(--paper);
  border: none;
  padding: 9px 16px;
  border-radius: var(--radius);
  font-family: var(--font-body);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  display: inline-block;
}
.buy-btn:hover { background: var(--marigold); color: var(--ink); }
.bundle-banner {
  background: var(--navy-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 14px;
  margin-bottom: 32px;
}
.bundle-banner .price { font-family: var(--font-mono); font-size: 20px; color: var(--marigold); }

@media (max-width: 640px) {
  .nav-links { display: none; }
  .hero { padding: 48px 0 36px; }
  .circuit-bg { display: none; }
}