* {
  box-sizing: border-box;
}
html {
  scroll-behavior: smooth;
  scroll-padding-top: 30px;
}
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.7 var(--font);
}
a {
  color: var(--accent);
  text-underline-offset: 4px;
}
main,
footer {
  max-width: 1160px;
  margin: auto;
  padding: 24px;
}
.intro {
  padding: 60px 0 48px;
  max-width: 830px;
}
.eyebrow {
  font-size: 11px;
  letter-spacing: 2px;
  font-weight: 750;
  color: var(--accent);
}
h1 {
  font-size: clamp(36px, 6vw, 64px);
  line-height: 1.12;
  letter-spacing: -2.5px;
  margin: 18px 0 24px;
}
h1 em {
  font-style: normal;
  color: var(--accent);
}
.intro p {
  font-size: 20px;
  color: var(--text-2);
  max-width: 700px;
}
.intro-meta {
  font-size: 13px;
  color: var(--text-2);
}
.layout {
  display: grid;
  grid-template-columns: 225px minmax(0, 1fr);
  gap: 48px;
}
.layout > nav {
  position: sticky;
  top: 90px;
  align-self: start;
}
.layout > nav a {
  display: block;
  color: var(--text-2);
  padding: 7px 0;
  text-decoration: none;
  font-size: 13px;
}
.layout > nav a:hover,
.layout > nav a[aria-current] {
  color: var(--accent);
}
.progress {
  border-top: 1px solid var(--line-2);
  margin-top: 20px;
  padding-top: 20px;
  font-size: 12px;
}
.progress label {
  display: block;
}
.progress span {
  float: right;
}
progress {
  width: 100%;
  height: 6px;
  accent-color: var(--accent);
}
.lesson {
  padding: 0 0 42px;
  margin-bottom: 35px;
  border-bottom: 1px solid var(--line-2);
}
h2 {
  font-size: 28px;
  line-height: 1.25;
  letter-spacing: -0.7px;
  margin: 10px 0 18px;
}
h3 {
  font-size: 18px;
  line-height: 1.4;
  margin: 0 0 8px;
}
p {
  margin: 0 0 16px;
}
.lead {
  color: var(--text-2);
  font-size: 18px;
}
.grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}
.card,
.lab,
.callout {
  background: var(--surface);
  border: 1px solid var(--line-2);
  border-radius: 14px;
  padding: 22px;
  margin: 18px 0;
}
.grid .card {
  margin: 0;
}
.card p:last-child,
.callout p:last-child {
  margin-bottom: 0;
}
.callout {
  background: var(--accent-soft);
  border-color: transparent;
}
.tag {
  font-size: 11px;
  letter-spacing: 1px;
  font-weight: 700;
  color: var(--accent);
}
.controls {
  display: flex;
  gap: 10px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 18px;
}
button,
select,
input {
  font: inherit;
}
button,
select {
  border: 1px solid var(--line-2);
  background: var(--surface);
  color: var(--text);
  border-radius: 8px;
  padding: 9px 13px;
}
button {
  cursor: pointer;
}
main button[aria-pressed="true"] {
  background: var(--accent);
  color: var(--on-accent);
}
button:hover {
  border-color: var(--accent);
}
:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 4px;
}
.chart {
  width: 100%;
  height: auto;
  display: block;
}
.chart text {
  fill: var(--text-2);
  font-size: 11px;
}
.chart .axis {
  stroke: var(--line-2);
}
.chart .up {
  stroke: var(--strong);
  fill: var(--strong);
}
.chart .down {
  stroke: var(--danger);
  fill: var(--danger);
}
.caption {
  font-size: 13px;
  color: var(--text-2);
  margin-top: 14px;
}
.readout {
  padding: 14px;
  border-radius: 8px;
  background: var(--surface-2);
  margin-top: 14px;
}
.table-wrap {
  overflow-x: auto;
}
table {
  border-collapse: collapse;
  width: 100%;
  font-size: 14px;
}
th,
td {
  text-align: left;
  padding: 13px 12px;
  border-bottom: 1px solid var(--line-2);
  vertical-align: top;
}
th {
  font-weight: 650;
  color: var(--text-2);
}
details {
  border-bottom: 1px solid var(--line-2);
  padding: 16px 0;
}
summary {
  cursor: pointer;
  font-weight: 650;
}
details p {
  margin: 12px 0;
}
.check {
  display: flex;
  gap: 12px;
  margin: 12px 0;
  align-items: start;
}
.check input {
  margin-top: 8px;
  accent-color: var(--accent);
}
.sources {
  margin: 30px 0 0;
  padding: 30px;
  background: var(--surface-2);
  border-radius: 14px;
  font-size: 14px;
}
.sources a {
  display: inline-block;
  margin: 0 18px 12px 0;
}
footer {
  font-size: 13px;
  color: var(--text-2);
}
.benchmark label {
  display: block;
  margin: 12px 0;
}
.benchmark input {
  width: 100%;
  accent-color: var(--accent);
}
.value {
  font-weight: 700;
  color: var(--accent);
}
@media (max-width: 800px) {
  .layout {
    grid-template-columns: 1fr;
    gap: 24px;
  }
  .layout > nav {
    position: static;
    border: 1px solid var(--line-2);
    border-radius: 12px;
    padding: 16px;
  }
  #lesson-nav {
    display: grid;
    grid-template-columns: 1fr 1fr;
  }
  .intro {
    padding-top: 35px;
  }
  .grid {
    grid-template-columns: 1fr;
  }
  main,
  footer {
    padding: 18px;
  }
  .lab {
    padding: 14px;
  }
}
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}
.teaching-diagram {
  margin: 18px 0;
  padding: 14px;
  background: var(--surface-2);
  border: 1px solid var(--line-2);
  border-radius: 10px;
}
.teaching-diagram svg {
  display: block;
  width: 100%;
  height: auto;
  max-width: 560px;
  margin: auto;
}
.teaching-diagram text {
  fill: var(--text-2);
  font: 13px var(--font);
}
.teaching-diagram .axis {
  stroke: var(--text-3);
}
.diagram-box {
  fill: var(--accent-soft);
  stroke: var(--line-2);
}
.teaching-diagram figcaption {
  font-size: 13px;
  line-height: 1.65;
  color: var(--text-2);
  margin-top: 12px;
}
.teaching-diagram figcaption strong {
  color: var(--text);
}
.diagram-gallery {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
  margin-top: 18px;
}
.diagram-gallery .teaching-diagram {
  margin: 0;
  height: 100%;
}
.diagram-gallery > div h3 {
  margin-top: 12px;
}
.diagram-gallery > div .teaching-diagram {
  height: auto;
}
.card > .teaching-diagram {
  padding: 10px;
}
#candles details > p.caption {
  margin-top: 18px;
}
@media (max-width: 650px) {
  .diagram-gallery {
    grid-template-columns: 1fr;
  }
  .teaching-diagram {
    padding: 12px;
  }
  .teaching-diagram text {
    font-size: 14px;
  }
}
.tooltip-hint {
  font-size: 14px !important;
  color: var(--text-2);
}
.learning-shortcuts {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin: 22px 0;
}
.learning-shortcuts a {
  background: var(--accent-soft);
  border: 1px solid var(--line-2);
  border-radius: 8px;
  padding: 10px 15px;
  font-size: 14px;
  font-weight: 650;
  text-decoration: none;
}
.learning-shortcuts a:first-child {
  background: var(--accent);
  color: var(--on-accent);
}
#lesson-menu {
  padding: 0;
  border: 0;
}
#lesson-menu > summary {
  font-size: 13px;
  color: var(--text-2);
  margin-bottom: 12px;
}
.walkthrough-navigation {
  display: flex;
  gap: 12px;
  align-items: center;
  justify-content: space-between;
  margin: 16px 0;
}
.walkthrough-navigation span {
  font-size: 13px;
  color: var(--text-2);
}
button:disabled {
  opacity: 0.45;
  cursor: default;
}
.related-lessons {
  font-size: 13px;
  margin-top: 18px;
}
.related-lessons a {
  white-space: nowrap;
}
footer {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
@media (max-width: 800px) {
  #walkthrough-controls {
    display: none;
  }
  .walkthrough-navigation {
    position: sticky;
    top: 0;
    background: var(--surface);
    padding: 10px 0;
    z-index: 2;
  }
  .intro-meta {
    line-height: 1.7;
  }
}

@media (max-width: 800px) {
  #walkthrough-chart text {
    font-size: 24px;
  }
  .chart:not(#walkthrough-chart) text {
    font-size: 16px;
  }
}