:root {
  color-scheme: light;
  --bg: #f6f4f1;
  --panel: #ffffff;
  --panel-strong: #eef2f4;
  --text: #1e272e;
  --muted: #64707a;
  --line: #d8dde0;
  --accent: #c9362c;
  --accent-strong: #8e211b;
  --blue: #1f5d8f;
  --shadow: 0 18px 48px rgba(22, 30, 38, 0.14);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.5;
}

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

button,
a {
  font: inherit;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 18px clamp(18px, 4vw, 48px);
  background: rgba(246, 244, 241, 0.92);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(14px);
}

.app-header h1,
.intro h2,
.section-heading h2,
.quiz-section h2 {
  margin: 0;
  line-height: 1.1;
}

.app-header h1 {
  font-size: clamp(1.55rem, 3vw, 2.4rem);
}

.eyebrow {
  margin: 0 0 6px;
  color: var(--accent-strong);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

nav {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 4px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 999px;
}

.nav-link {
  min-width: 86px;
  padding: 9px 14px;
  color: var(--muted);
  text-align: center;
  text-decoration: none;
  border-radius: 999px;
}

.nav-link.active {
  color: #ffffff;
  background: var(--text);
}

.nav-link.disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

main {
  width: min(1440px, 100%);
  margin: 0 auto;
  padding: 30px clamp(16px, 4vw, 48px) 56px;
}

.intro {
  max-width: 760px;
  margin-bottom: 22px;
}

.intro h2,
.section-heading h2,
.quiz-section h2 {
  font-size: clamp(1.35rem, 2.2vw, 2rem);
}

.intro p,
.quiz-task p,
.card-copy p {
  margin: 8px 0 0;
  color: var(--muted);
}

.truck-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.trainer-card,
.quiz-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.trainer-card {
  overflow: hidden;
}

.card-copy {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 18px;
}

.card-copy h3 {
  margin: 0;
  font-size: 1.1rem;
}

.card-copy p {
  min-width: 96px;
  text-align: right;
}

.image-button {
  position: relative;
  display: block;
  width: 100%;
  padding: 0;
  overflow: hidden;
  color: inherit;
  background: #111820;
  border: 0;
  cursor: pointer;
}

.image-button img {
  width: 100%;
  aspect-ratio: 4 / 3;
  object-fit: cover;
  transition: transform 220ms ease, opacity 180ms ease;
}

.image-button:hover img,
.image-button:focus-visible img {
  transform: scale(1.015);
}

.image-button:focus-visible {
  outline: 4px solid var(--blue);
  outline-offset: -4px;
}

.image-badge {
  position: absolute;
  right: 14px;
  bottom: 14px;
  padding: 8px 12px;
  color: #ffffff;
  background: rgba(30, 39, 46, 0.86);
  border-radius: 999px;
  font-size: 0.9rem;
  font-weight: 800;
}

.trainer-card.is-open .image-badge {
  background: rgba(201, 54, 44, 0.92);
}

.reference-section {
  margin-top: 42px;
}

.section-heading {
  margin-bottom: 16px;
}

.reference-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
}

figure {
  margin: 0;
  overflow: hidden;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.reference-media {
  position: relative;
  overflow: hidden;
  background: #111820;
}

.reference-media img {
  width: 100%;
  height: auto;
}

.reference-card {
  min-height: 100%;
}

.reference-mask {
  position: absolute;
  left: var(--mask-left);
  top: var(--mask-top);
  display: grid;
  width: var(--mask-width);
  height: var(--mask-height);
  min-height: 96px;
  padding: 18px;
  place-items: center;
  align-content: center;
  gap: 8px;
  color: #ffffff;
  text-align: center;
  background:
    linear-gradient(135deg, rgba(18, 25, 32, 0.98), rgba(38, 45, 52, 0.96)),
    repeating-linear-gradient(
      -45deg,
      rgba(255, 255, 255, 0.04),
      rgba(255, 255, 255, 0.04) 10px,
      rgba(255, 255, 255, 0.1) 10px,
      rgba(255, 255, 255, 0.1) 20px
    );
  border: 2px solid rgba(255, 212, 77, 0.88);
  border-radius: 8px;
  cursor: pointer;
  box-shadow: 0 14px 40px rgba(0, 0, 0, 0.32);
}

.reference-mask:hover,
.reference-mask:focus-visible {
  border-color: #ffffff;
}

.reference-mask:focus-visible {
  outline: 4px solid var(--blue);
  outline-offset: 3px;
}

.reference-mask span {
  color: #ffd44d;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

.reference-mask strong {
  font-size: clamp(0.9rem, 1.5vw, 1.15rem);
}

.reference-card.is-uncovered .reference-mask {
  left: auto;
  top: 12px;
  right: 12px;
  width: auto;
  height: auto;
  min-height: 0;
  padding: 9px 12px;
  gap: 2px;
  background: rgba(30, 39, 46, 0.9);
  border-color: rgba(255, 255, 255, 0.8);
  border-radius: 999px;
  box-shadow: 0 8px 22px rgba(0, 0, 0, 0.28);
}

.reference-card.is-uncovered .reference-mask span {
  font-size: 0.68rem;
}

.reference-card.is-uncovered .reference-mask strong {
  font-size: 0.82rem;
}

figcaption {
  padding: 12px 14px;
  color: var(--muted);
  font-weight: 700;
}

.quiz-section {
  margin-top: 42px;
}

.quiz-layout {
  display: grid;
  grid-template-columns: minmax(260px, 360px) minmax(0, 1fr);
  gap: 18px;
  align-items: start;
}

.quiz-card {
  overflow: hidden;
}

.quiz-task {
  padding: 20px;
}

.quiz-meta {
  margin: 0 0 8px;
  color: var(--accent-strong);
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
}

.quiz-task h3 {
  margin: 0;
  font-size: clamp(1.25rem, 2vw, 1.75rem);
  line-height: 1.15;
}

.quiz-actions {
  display: grid;
  gap: 10px;
  margin-top: 18px;
}

.quiz-nav-buttons {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.quiz-actions button,
.quiz-area-grid button,
.quiz-overview button {
  min-height: 44px;
  padding: 0 14px;
  color: var(--text);
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  cursor: pointer;
}

.quiz-actions button:hover:not(:disabled),
.quiz-area-grid button:hover,
.quiz-overview button:hover {
  border-color: var(--text);
}

.quiz-actions button:disabled {
  cursor: not-allowed;
  opacity: 0.48;
}

#checkAnswer {
  color: #ffffff;
  background: var(--text);
  border-color: var(--text);
}

.quiz-overview {
  margin-top: 18px;
}

.quiz-overview h4 {
  margin: 0 0 10px;
  font-size: 0.9rem;
}

.quiz-overview ol {
  display: grid;
  gap: 6px;
  max-height: 320px;
  margin: 0;
  padding: 0;
  overflow: auto;
  list-style: none;
}

.quiz-overview button {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 8px;
  width: 100%;
  min-height: 38px;
  padding: 6px 10px;
  text-align: left;
}

.quiz-overview button.is-current {
  border-color: var(--blue);
  box-shadow: 0 0 0 2px rgba(31, 93, 143, 0.16);
}

.quiz-overview button.is-correct {
  color: #17603d;
  background: #edf8f2;
  border-color: rgba(25, 122, 74, 0.42);
}

.quiz-overview button.is-wrong {
  color: var(--accent-strong);
  background: #fff2f0;
  border-color: rgba(201, 54, 44, 0.42);
}

.quiz-overview span:first-child {
  color: var(--muted);
  font-weight: 900;
}

.quiz-feedback {
  min-height: 86px;
  margin-top: 18px;
  padding: 14px;
  color: var(--muted);
  background: #f8fafb;
  border: 1px solid var(--line);
  border-radius: 8px;
  font-weight: 700;
}

.quiz-feedback.is-correct {
  color: #17603d;
  background: #edf8f2;
  border-color: rgba(25, 122, 74, 0.36);
}

.quiz-feedback.is-wrong {
  color: var(--accent-strong);
  background: #fff2f0;
  border-color: rgba(201, 54, 44, 0.34);
}

.quiz-area-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
  padding: 18px;
  border-bottom: 1px solid var(--line);
}

.quiz-area-grid button.is-selected {
  color: #ffffff;
  background: var(--blue);
  border-color: var(--blue);
}

.quiz-stage-shell {
  padding: 18px;
}

.quiz-stage {
  position: relative;
  display: grid;
  min-height: 420px;
  overflow: hidden;
  place-items: center;
  background: #151b21;
  border: 1px solid var(--line);
  border-radius: 8px;
  cursor: default;
  user-select: none;
}

.quiz-stage.has-image {
  display: block;
  min-height: 0;
  cursor: crosshair;
}

.quiz-stage img {
  display: none;
  width: 100%;
  height: auto;
}

.quiz-stage.has-image img {
  display: block;
}

.quiz-empty-state {
  padding: 24px;
  color: #dce2e6;
  text-align: center;
}

.quiz-stage.has-image .quiz-empty-state {
  display: none;
}

.quiz-overlay {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

.quiz-overlay polygon {
  fill: rgba(25, 122, 74, 0.24);
  stroke: #29b36f;
  stroke-width: 0.55;
  vector-effect: non-scaling-stroke;
}

.quiz-mask {
  position: absolute;
  left: var(--mask-left, 10%);
  top: var(--mask-top, 8%);
  display: grid;
  width: var(--mask-width, 80%);
  height: var(--mask-height, 70%);
  min-height: 92px;
  padding: 18px;
  place-items: center;
  color: #ffd44d;
  text-align: center;
  background:
    linear-gradient(135deg, rgba(18, 25, 32, 0.98), rgba(38, 45, 52, 0.96)),
    repeating-linear-gradient(
      -45deg,
      rgba(255, 255, 255, 0.04),
      rgba(255, 255, 255, 0.04) 10px,
      rgba(255, 255, 255, 0.1) 10px,
      rgba(255, 255, 255, 0.1) 20px
    );
  border: 2px solid rgba(255, 212, 77, 0.9);
  border-radius: 8px;
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0;
  text-transform: uppercase;
  pointer-events: none;
  box-shadow: 0 14px 40px rgba(0, 0, 0, 0.32);
}

.quiz-mask[hidden] {
  display: none;
}

.quiz-guess-marker {
  position: absolute;
  width: 22px;
  height: 22px;
  background: var(--accent);
  border: 3px solid #ffffff;
  border-radius: 999px;
  pointer-events: none;
  transform: translate(-50%, -50%);
  box-shadow: 0 8px 18px rgba(0, 0, 0, 0.36);
}

@media (max-width: 900px) {
  .truck-grid,
  .reference-grid,
  .quiz-layout {
    grid-template-columns: 1fr;
  }

  .reference-grid {
    max-width: 680px;
  }

  .quiz-task {
    order: 2;
  }

  .quiz-workspace {
    order: 1;
  }

  .quiz-overview ol {
    grid-template-columns: repeat(6, minmax(0, 1fr));
    max-height: none;
  }

  .quiz-overview button {
    grid-template-columns: 1fr;
    min-height: 44px;
    padding: 6px;
    text-align: center;
  }

  .quiz-overview button span:last-child {
    display: none;
  }
}

@media (max-width: 680px) {
  .app-header {
    align-items: stretch;
    flex-direction: column;
  }

  nav {
    align-self: flex-start;
    width: 100%;
    justify-content: space-between;
    gap: 4px;
    border-radius: 8px;
  }

  .nav-link {
    min-width: 0;
    flex: 1;
    padding: 10px 8px;
  }

  .nav-mapper {
    display: none;
  }

  main {
    padding: 20px 10px 36px;
  }

  .intro {
    margin-bottom: 16px;
  }

  .truck-grid,
  .reference-grid,
  .quiz-layout {
    gap: 12px;
  }

  .card-copy {
    align-items: start;
    flex-direction: column;
    gap: 2px;
  }

  .card-copy p {
    min-width: 0;
    text-align: left;
  }

  .image-badge {
    right: 10px;
    bottom: 10px;
    padding: 7px 10px;
    font-size: 0.82rem;
  }

  .reference-section,
  .quiz-section {
    margin-top: 30px;
  }

  .quiz-task,
  .quiz-stage-shell,
  .quiz-area-grid {
    padding: 12px;
  }

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

  .quiz-area-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 8px;
  }

  .quiz-actions button,
  .quiz-area-grid button {
    min-height: 48px;
  }

  .quiz-stage {
    min-height: 260px;
    border-radius: 6px;
  }

  .quiz-overview ol {
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }

  .quiz-overview button {
    min-height: 40px;
    padding: 4px;
  }

  .quiz-feedback {
    min-height: 0;
    margin-top: 14px;
  }
}

@media (max-width: 420px) {
  .quiz-area-grid {
    grid-template-columns: 1fr;
  }

  .quiz-overview ol {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}