.top-nav {
  position: sticky;
  top: 0;
  z-index: 5;
  display: flex;
  gap: var(--spacing-md);
  background: rgba(10, 14, 26, 0.95);
  border-bottom: 1px solid rgba(0, 212, 255, 0.25);
  padding: var(--spacing-sm) var(--spacing-md);
  backdrop-filter: blur(4px);
}

.nav__link {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  color: var(--color-text);
  text-decoration: none;
  border-radius: var(--radius-sm);
  padding: 0 var(--spacing-sm);
}

.nav__link:hover,
.nav__link:focus-visible {
  text-decoration: underline;
  box-shadow: var(--glow-spread) var(--glow-color);
}

.hero {
  display: grid;
  gap: var(--spacing-lg);
  align-items: center;
}

.hero__visual {
  border: 1px solid rgba(0, 212, 255, 0.25);
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg, rgba(0, 212, 255, 0.2), rgba(123, 47, 255, 0.22));
  padding: var(--spacing-xl);
}

.section {
  background: rgba(19, 25, 41, 0.88);
  border: 1px solid rgba(138, 155, 191, 0.25);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
}

.section__grid {
  display: grid;
  gap: var(--spacing-md);
}

.infobox {
  background: var(--color-surface);
  border: 1px solid rgba(138, 155, 191, 0.35);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
}

.infobox__title {
  margin-bottom: var(--spacing-sm);
}

.infobox--merksatz {
  border-color: rgba(0, 212, 255, 0.5);
  background: linear-gradient(160deg, rgba(0, 212, 255, 0.14), rgba(19, 25, 41, 0.95));
  box-shadow: var(--glow-spread) var(--glow-color);
}

.infobox--merksatz:hover {
  box-shadow: 0 0 1.25rem rgba(0, 212, 255, 0.5);
}

.reaction-schema {
  border: 1px solid rgba(123, 47, 255, 0.5);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  background: var(--color-surface-elevated);
  overflow-x: auto;
}

.quiz-card {
  border: 1px solid rgba(0, 212, 255, 0.25);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  background: var(--color-surface);
}

.quiz-card__answers {
  display: grid;
  gap: var(--spacing-sm);
}

.btn {
  width: 100%;
  min-height: 44px;
  border: 1px solid rgba(0, 212, 255, 0.6);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-text);
  font: inherit;
  text-align: left;
  padding: 0.65rem 0.85rem;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, opacity 0.2s ease;
}

.btn:hover {
  transform: scale(1.02);
  box-shadow: var(--glow-spread) var(--glow-color);
}

.btn:active {
  transform: scale(0.98);
}

.btn:disabled,
.btn[aria-disabled="true"] {
  opacity: 0.5;
  cursor: not-allowed;
  box-shadow: none;
}

.quiz__button--correct {
  border-color: var(--color-correct);
  background: rgba(0, 230, 118, 0.18);
  box-shadow: 0 0 0.8rem rgba(0, 230, 118, 0.35);
}

.quiz__button--wrong {
  border-color: var(--color-wrong);
  background: rgba(255, 68, 68, 0.2);
}

.cta-btn {
  text-align: center;
  text-decoration: none;
  font-weight: 700;
  color: var(--color-bg);
  background: linear-gradient(90deg, var(--color-accent), #7df0ff);
}

.score-card {
  border: 1px solid rgba(0, 212, 255, 0.4);
  border-radius: var(--radius-md);
  background: var(--color-surface-elevated);
  padding: var(--spacing-md);
}