:root {
  color-scheme: light;
  --ink: #24385f;
  --muted: #6d7891;
  --line: #cfd6e4;
  --panel: #ffffff;
  --page: #eef2fa;
  --choice: #d9dee9;
  --choice-hover: #e7ebf3;
  --blue: #2f6eb3;
  --green: #45a65a;
  --green-soft: #b4dfb8;
  --red: #c94f5b;
  --red-soft: #f3c5c9;
  --shadow: 0 12px 28px rgba(39, 54, 88, 0.14);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html {
  min-height: 100%;
}
body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background: var(--page);
  overflow-x: hidden;
}
button {
  border: 0;
  color: inherit;
  font: inherit;
  cursor: pointer;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}
button:disabled { cursor: not-allowed; opacity: 0.55; }
.topbar {
  display: grid;
  grid-template-columns: 76px 140px 140px repeat(5, minmax(120px, 180px));
  align-items: stretch;
  min-height: 70px;
  background: #fff;
  border-bottom: 1px solid var(--line);
  overflow-x: auto;
}
.brand-cell, .stat-cell, .timer-cell, .mode-tab {
  display: grid;
  place-items: center;
  border-right: 1px solid var(--line);
  background: #fff;
}
.seal {
  display: grid;
  place-items: center;
  width: 48px;
  height: 48px;
  border: 4px solid #0877a7;
  border-radius: 50%;
  color: #f6c546;
  background: #165d9a;
  font-weight: 800;
  font-size: 13px;
}
.mode-tab {
  gap: 2px;
  padding: 0 16px;
  font-weight: 700;
  color: var(--muted);
}
.mode-tab.active {
  color: var(--ink);
  box-shadow: inset 0 -4px 0 var(--blue);
}
.stat-cell strong {
  display: block;
  font-size: 20px;
  line-height: 1.1;
  font-weight: 500;
}
.stat-cell span {
  display: block;
  margin-top: 4px;
  font-size: 14px;
  text-align: center;
  white-space: nowrap;
}
.stat-cell.good strong { color: #06a529; }
.stat-cell.bad strong { color: #b4000b; }
.timer-cell {
  font-size: 31px;
  letter-spacing: 0;
  white-space: nowrap;
}
.app-shell {
  min-height: calc(100vh - 152px);
  padding: 72px 28px 100px;
}
.quiz-panel {
  width: min(1120px, 100%);
  margin: 0 auto;
}
.question-meta {
  display: flex;
  justify-content: center;
  gap: 18px;
  margin-bottom: 16px;
  color: var(--muted);
  font-size: 14px;
  font-weight: 700;
  text-transform: uppercase;
}
h1 {
  max-width: 980px;
  min-height: 78px;
  margin: 0 auto 28px;
  text-align: center;
  font-size: 30px;
  line-height: 1.35;
  font-weight: 500;
  letter-spacing: 0;
}
.pdf-note {
  max-width: 760px;
  margin: -14px auto 24px;
  padding: 12px 16px;
  border: 1px solid #d7c67a;
  background: #fff7d6;
  color: #675a18;
  border-radius: 6px;
  text-align: center;
}
.answer-layout {
  display: grid;
  grid-template-columns: minmax(320px, 1fr) 280px;
  gap: 36px;
  align-items: start;
}
.answers {
  display: grid;
  gap: 18px;
}
.answer-btn {
  display: grid;
  grid-template-columns: 90px 1fr;
  min-height: 92px;
  padding: 0;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--panel);
  box-shadow: 0 3px 8px rgba(36, 56, 95, 0.08);
  overflow: hidden;
  text-align: left;
}
.answer-btn:hover { background: var(--choice-hover); }
.answer-letter {
  display: grid;
  place-items: center;
  min-height: 92px;
  background: var(--choice);
  font-size: 36px;
  font-weight: 800;
}
.answer-text {
  display: flex;
  align-items: center;
  min-width: 0;
  padding: 20px 30px;
  font-size: 18px;
  line-height: 1.45;
  overflow-wrap: anywhere;
}
.answer-text.has-answer-image {
  padding-top: 14px;
  padding-bottom: 14px;
}
.answer-image {
  display: block;
  max-width: 100%;
  max-height: 60px;
  width: auto;
  height: auto;
  object-fit: contain;
}
.answer-image-fallback {
  color: var(--blue);
  font-weight: 700;
  text-decoration: underline;
  text-underline-offset: 3px;
}
.answer-btn.selected {
  border-color: var(--blue);
  box-shadow: 0 0 0 2px rgba(47, 110, 179, 0.18);
}
.answer-btn.selected .answer-letter {
  color: #fff;
  background: var(--blue);
}
.answer-btn.correct {
  border-color: var(--green);
  background: #f1fbf2;
}
.answer-btn.correct .answer-letter {
  color: #fff;
  background: var(--green);
}
.answer-btn.wrong {
  border-color: var(--red);
  background: #fff4f5;
}
.answer-btn.wrong .answer-letter {
  color: #fff;
  background: var(--red);
}
.side-panel {
  display: grid;
  gap: 18px;
}
.score-card {
  min-height: 116px;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #fff;
  box-shadow: var(--shadow);
}
.score-card span {
  color: var(--muted);
  font-size: 14px;
  text-transform: uppercase;
  font-weight: 700;
}
.score-card strong {
  display: block;
  margin-top: 8px;
  font-size: 42px;
  font-weight: 600;
}
.progress-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
  max-height: 390px;
  overflow: auto;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #fff;
}
.grid-btn {
  aspect-ratio: 1;
  border-radius: 4px;
  background: #eef2f8;
  color: var(--ink);
  font-weight: 700;
  font-size: 13px;
}
.grid-btn.current { outline: 3px solid var(--blue); }
.grid-btn.done { background: var(--green-soft); }
.grid-btn.miss { background: var(--red-soft); }
.grid-btn.flag { box-shadow: inset 0 -4px 0 #d5ad22; }
.actionbar {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  justify-content: center;
  gap: 20px;
  padding: 20px;
  background: #fff;
  border-top: 1px solid var(--line);
  z-index: 5;
}
.actionbar button, .result-actions button {
  min-width: 210px;
  min-height: 54px;
  padding: 0 22px;
  border-radius: 6px;
  font-weight: 700;
}
.ghost { border: 1px solid var(--line); background: #fff; }
.secondary { border: 1px solid #e6d5d7; background: #fff; color: #c76b72; }
.primary { background: var(--green-soft); color: #fff; }
.primary:not(:disabled):hover { background: #8fcf95; }
.hidden { display: none !important; }
.result-modal {
  position: fixed;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 24px;
  background: rgba(20, 31, 54, 0.48);
  z-index: 10;
}
.result-card {
  width: min(520px, 100%);
  padding: 30px;
  border-radius: 8px;
  background: #fff;
  box-shadow: 0 30px 80px rgba(0,0,0,0.25);
}
.result-card h2 { margin: 0 0 12px; font-size: 28px; }
.result-card p { color: var(--muted); line-height: 1.6; }
.result-actions { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 24px; }
@media (max-width: 980px) {
  .topbar {
    position: sticky;
    top: 0;
    z-index: 6;
    grid-template-columns: 64px repeat(2, minmax(0, 1fr));
    min-height: auto;
    overflow: visible;
    box-shadow: 0 8px 22px rgba(36, 56, 95, 0.08);
  }
  .brand-cell,
  .mode-tab {
    min-height: 64px;
  }
  .stat-cell,
  .timer-cell {
    min-height: 58px;
    border-top: 1px solid var(--line);
  }
  .stat-cell {
    padding: 8px 6px;
  }
  .stat-cell strong {
    font-size: 19px;
  }
  .stat-cell span {
    font-size: 12px;
    line-height: 1.2;
    white-space: normal;
  }
  .timer-cell {
    font-size: 25px;
  }
  .app-shell { padding-top: 34px; }
  .answer-layout { grid-template-columns: 1fr; }
  .side-panel { grid-template-columns: 1fr; }
  .progress-grid { grid-template-columns: repeat(10, 1fr); max-height: 180px; }
}
@media (max-width: 680px) {
  .topbar {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  .brand-cell {
    grid-column: 1;
    min-height: 52px;
  }
  .mode-tab[data-mode="learn"] {
    grid-column: 2 / 3;
  }
  .mode-tab[data-mode="exam"] {
    grid-column: 3 / 5;
  }
  .mode-tab {
    min-height: 52px;
    padding: 0 8px;
    font-size: 14px;
  }
  .seal {
    width: 40px;
    height: 40px;
    border-width: 3px;
    font-size: 11px;
  }
  .topbar > :nth-child(4) { grid-column: 1; grid-row: 2; }
  .topbar > :nth-child(5) { grid-column: 2; grid-row: 2; }
  .topbar > :nth-child(7) { grid-column: 3; grid-row: 2; }
  .topbar > :nth-child(8) { grid-column: 4; grid-row: 2; }
  .timer-cell {
    grid-column: 1 / -1;
    grid-row: 3;
    min-height: 42px;
    font-size: 25px;
    font-weight: 500;
  }
  .stat-cell {
    min-height: 52px;
    padding: 5px 4px;
    border-right: 1px solid var(--line);
  }
  .stat-cell strong {
    font-size: 17px;
  }
  .stat-cell span {
    max-width: 74px;
    font-size: 10px;
  }
  .app-shell {
    min-height: auto;
    padding: 20px 12px 176px;
  }
  .question-meta {
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 12px;
    padding: 0 2px;
    font-size: 12px;
  }
  h1 {
    min-height: auto;
    margin-bottom: 16px;
    text-align: left;
    font-size: 21px;
    line-height: 1.32;
  }
  .pdf-note {
    margin: -8px 0 16px;
    font-size: 13px;
    text-align: left;
  }
  .answer-layout {
    gap: 18px;
  }
  .answers {
    gap: 10px;
  }
  .answer-btn {
    grid-template-columns: 56px 1fr;
    min-height: 70px;
    border-radius: 7px;
  }
  .answer-letter {
    min-height: 70px;
    font-size: 27px;
  }
  .answer-text {
    padding: 15px 14px;
    font-size: 15px;
    line-height: 1.4;
  }
  .score-card {
    min-height: 74px;
    padding: 14px 16px;
  }
  .score-card strong {
    margin-top: 2px;
    font-size: 30px;
  }
  .progress-grid {
    grid-template-columns: repeat(7, minmax(34px, 1fr));
    gap: 6px;
    max-height: 156px;
    padding: 10px;
  }
  .grid-btn {
    min-width: 34px;
    font-size: 12px;
  }
  .actionbar {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    padding: 12px;
    padding-bottom: calc(12px + env(safe-area-inset-bottom));
  }
  .actionbar button,
  .result-actions button {
    min-width: 0;
    min-height: 50px;
    padding: 0 10px;
    font-size: 13px;
    line-height: 1.15;
  }
  .result-modal {
    padding: 14px;
  }
  .result-card {
    padding: 22px;
  }
  .result-card h2 {
    font-size: 23px;
  }
  .result-actions {
    display: grid;
    grid-template-columns: 1fr;
  }
}
@media (max-width: 380px) {
  .stat-cell span {
    font-size: 10px;
  }
  .mode-tab {
    font-size: 13px;
  }
  h1 {
    font-size: 20px;
  }
  .answer-btn {
    grid-template-columns: 50px 1fr;
  }
  .answer-letter {
    font-size: 25px;
  }
  .answer-text {
    font-size: 14px;
  }
}

/* ── Ad Slots ── */

/* Base: all ad containers get subtle styling */
.ad-slot {
  position: relative;
  border-radius: 6px;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

.ad-slot ins {
  position: relative;
  z-index: 1;
  width: 100%;
}

/* Top Banner — highly visible on load above content */
.ad-top {
  max-width: 980px;
  margin: 16px auto 0;
  min-height: 90px;
  width: calc(100% - 56px);
}

/* Sidebar ad — sits above the score card on desktop */
.ad-sidebar {
  margin-bottom: 4px;
  min-height: 250px;
}

/* Between-questions ad — horizontal banner shown after answer reveal */
.ad-between {
  max-width: 728px;
  margin: 28px auto 0;
  min-height: 90px;
}

/* Result modal ad — natural pause moment */
.ad-result {
  margin: 18px 0 6px;
  min-height: 100px;
}

/* Hide sidebar ad on mobile — avoid cluttering the small screen */
@media (max-width: 980px) {
  .ad-sidebar {
    display: none;
  }
  .ad-between {
    max-width: 100%;
    margin-top: 18px;
  }
}