:root {
  --bg: #f5f5f7;
  --surface: #ffffff;
  --ink: #1d1d1f;
  --muted: #626267;
  --line: #d2d2d7;
  --green: #087f5b;
  --green-soft: #e8f4ef;
  --orange: #b84a1b;
  --orange-soft: #f8ece6;
  --blue: #0071e3;
  --code-bg: #161618;
  --code-line: #28282c;
  --max-width: 1240px;
  --radius: 8px;
  --shadow: 0 20px 55px rgba(0, 0, 0, 0.10);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 70px;
}

body {
  margin: 0;
  min-width: 320px;
  color: var(--ink);
  background: var(--bg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  letter-spacing: 0;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: inherit;
  text-decoration: none;
}

button,
input {
  font: inherit;
  letter-spacing: 0;
}

button,
a,
input {
  -webkit-tap-highlight-color: transparent;
}

.skip-link {
  position: fixed;
  z-index: 1000;
  top: 8px;
  left: 8px;
  padding: 8px 12px;
  background: var(--ink);
  color: #fff;
  transform: translateY(-160%);
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  position: fixed;
  z-index: 100;
  top: 0;
  right: 0;
  left: 0;
  height: 62px;
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  background: rgba(250, 250, 252, 0.84);
  backdrop-filter: saturate(180%) blur(18px);
  -webkit-backdrop-filter: saturate(180%) blur(18px);
}

.site-nav {
  display: flex;
  align-items: center;
  width: min(calc(100% - 40px), var(--max-width));
  height: 100%;
  margin: 0 auto;
  gap: 28px;
}

.brand {
  display: inline-flex;
  align-items: center;
  flex-shrink: 0;
  gap: 9px;
  font-size: 15px;
  font-weight: 700;
}

.brand-mark {
  display: grid;
  width: 27px;
  height: 27px;
  place-items: center;
  border: 1px solid #b8b8bd;
  border-radius: 50%;
  color: var(--green);
  font-size: 17px;
  line-height: 1;
}

.nav-links {
  display: flex;
  margin-left: auto;
  gap: 28px;
  color: #48484a;
  font-size: 13px;
}

.nav-links a,
.directory-toggle {
  transition: color 180ms ease, background-color 180ms ease;
}

.nav-links a:hover,
.nav-links a:focus-visible {
  color: var(--blue);
}

.directory-toggle {
  display: inline-flex;
  align-items: center;
  flex-shrink: 0;
  gap: 6px;
  padding: 5px 13px;
  border: 1px solid #b8b8bd;
  border-radius: 999px;
  background: #fff;
  color: var(--ink);
  cursor: pointer;
  font-size: 13px;
  font-weight: 650;
}

.directory-toggle:hover,
.directory-toggle:focus-visible,
.directory-toggle[aria-expanded="true"] {
  border-color: var(--ink);
  background: var(--ink);
  color: #fff;
}

.directory-toggle span {
  font-size: 16px;
  transition: transform 220ms ease;
}

.directory-toggle[aria-expanded="true"] span {
  transform: rotate(180deg);
}

.directory-menu {
  position: absolute;
  z-index: 10;
  top: 54px;
  right: max(20px, calc((100vw - var(--max-width)) / 2));
  width: 310px;
  padding: 14px;
  border: 1px solid #d6d6da;
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.96);
  box-shadow: var(--shadow);
  backdrop-filter: blur(18px);
  animation: menu-in 220ms cubic-bezier(0.22, 1, 0.36, 1) both;
}

.directory-menu[hidden] {
  display: none;
}

.directory-menu > p {
  margin: 3px 8px 9px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}

.directory-menu a {
  display: grid;
  padding: 10px 8px;
  grid-template-columns: 42px 1fr;
  border-radius: 6px;
  font-size: 14px;
  transition: background-color 160ms ease, transform 160ms ease;
}

.directory-menu a:hover,
.directory-menu a:focus-visible {
  background: #f1f1f3;
  transform: translateX(2px);
}

.directory-menu a span {
  color: var(--green);
  font-weight: 750;
}

.scroll-progress {
  position: absolute;
  right: 0;
  bottom: -1px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--blue);
  transform-origin: left center;
}

.project-intro {
  position: relative;
  display: flex;
  align-items: flex-start;
  height: calc(100svh - 84px);
  min-height: 720px;
  margin-top: 62px;
  overflow: hidden;
  background-color: #f8f8fa;
  background-image: url("../programs/step01_linear_convection/figures/03_numerical_vs_exact.png");
  background-position: calc(100% + 90px - var(--hero-shift, 0px)) center;
  background-size: min(830px, 66vw) auto;
  background-repeat: no-repeat;
}

.project-intro::before {
  position: absolute;
  inset: 0;
  background: rgba(248, 248, 250, 0.82);
  content: "";
}

.intro-inner {
  position: relative;
  display: flex;
  min-height: 100%;
  flex-direction: column;
  justify-content: center;
  width: min(calc(100% - 40px), var(--max-width));
  margin: 0 auto;
  padding: 54px 0 46px;
  opacity: calc(1 - var(--hero-progress, 0) * 1.15);
  transform: translateY(calc(var(--hero-progress, 0) * -110px)) scale(calc(1 - var(--hero-progress, 0) * 0.035));
  transform-origin: left center;
  will-change: opacity, transform;
}

.eyebrow,
.lab-kicker,
.block-heading p {
  margin: 0 0 12px;
  color: var(--green);
  font-size: 13px;
  font-weight: 750;
  letter-spacing: 0;
}

.project-intro h1 {
  max-width: 850px;
  margin: 0;
  font-size: 72px;
  font-weight: 720;
  line-height: 1.02;
  letter-spacing: 0;
}

.intro-copy {
  max-width: 750px;
  margin: 28px 0 0;
  color: #424245;
  font-size: 21px;
  line-height: 1.55;
}

.intro-facts {
  display: grid;
  max-width: 800px;
  margin: 48px 0 0;
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.intro-facts div {
  padding: 0 22px;
  border-left: 1px solid rgba(0, 0, 0, 0.18);
}

.intro-facts div:first-child {
  padding-left: 0;
  border-left: 0;
}

.intro-facts dt {
  font-size: 27px;
  font-weight: 750;
  line-height: 1.2;
}

.intro-facts dd {
  margin: 5px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.scroll-cue {
  display: flex;
  align-items: center;
  margin-top: 34px;
  color: var(--muted);
  gap: 10px;
  font-size: 14px;
}

.scroll-cue i {
  position: relative;
  display: block;
  width: 21px;
  height: 34px;
  border: 1px solid #9e9ea4;
  border-radius: 999px;
}

.scroll-cue i::after {
  position: absolute;
  top: 7px;
  left: 8px;
  width: 3px;
  height: 7px;
  border-radius: 999px;
  background: var(--green);
  content: "";
  animation: scroll-dot 1.8s ease-in-out infinite;
}

.program-section {
  padding: 116px 20px 128px;
}

.program-linear {
  background: var(--surface);
}

.program-nonlinear {
  background: #f1f1f3;
}

.section-inner {
  width: min(100%, var(--max-width));
  margin: 0 auto;
}

.program-heading {
  display: grid;
  align-items: start;
  grid-template-columns: 190px minmax(0, 820px);
  gap: 42px;
}

.step-label {
  display: flex;
  align-items: center;
  gap: 12px;
  padding-top: 8px;
  color: var(--green);
  font-size: 14px;
  font-weight: 700;
}

.program-nonlinear .step-label,
.program-nonlinear .lab-kicker,
.program-nonlinear .block-heading p {
  color: var(--orange);
}

.step-label span {
  color: #aaaab0;
  font-size: 34px;
  font-weight: 350;
  line-height: 1;
}

.program-heading h2 {
  margin: 0;
  font-size: 52px;
  line-height: 1.1;
}

.program-heading p {
  max-width: 760px;
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 19px;
}

.equation-row {
  display: grid;
  margin: 54px 0 34px;
  grid-template-columns: 0.8fr 1.2fr;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.equation-row > div {
  min-width: 0;
  padding: 25px 28px;
  border-left: 1px solid var(--line);
}

.equation-row > div:first-child {
  padding-left: 0;
  border-left: 0;
}

.equation-row span {
  display: block;
  margin-bottom: 6px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 650;
}

.equation-row strong {
  display: block;
  overflow-wrap: anywhere;
  font-family: Cambria, "Times New Roman", serif;
  font-size: 23px;
  line-height: 1.45;
}

.explanation-grid {
  display: grid;
  margin: 0 0 34px;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.explanation-grid article {
  min-width: 0;
  padding: 27px 28px 30px;
  border-left: 1px solid var(--line);
}

.explanation-grid article:first-child {
  padding-left: 0;
  border-left: 0;
}

.explanation-grid span {
  color: var(--green);
  font-size: 14px;
  font-weight: 750;
}

.program-nonlinear .explanation-grid span {
  color: var(--orange);
}

.explanation-grid h3 {
  margin: 9px 0 8px;
  font-size: 21px;
}

.explanation-grid p {
  margin: 0;
  color: var(--muted);
  font-size: 16px;
  line-height: 1.75;
}

.simulation-lab {
  overflow: hidden;
  border: 1px solid #d7d7db;
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: 0 2px 0 rgba(0, 0, 0, 0.02);
  transition: box-shadow 300ms ease, transform 300ms ease;
}

.simulation-lab:focus-within,
.simulation-lab.is-running {
  box-shadow: var(--shadow);
  transform: translateY(-2px);
}

.lab-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 92px;
  padding: 18px 22px;
  border-bottom: 1px solid var(--line);
  gap: 24px;
}

.lab-toolbar h3 {
  margin: 0;
  font-size: 23px;
}

.lab-kicker {
  margin-bottom: 2px;
  font-size: 13px;
}

.lab-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.run-button,
.tool-button,
.copy-code,
.source-actions a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 38px;
  padding: 7px 13px;
  border: 1px solid #c8c8cd;
  border-radius: 6px;
  cursor: pointer;
  font-size: 13px;
  font-weight: 650;
  transition: border-color 180ms ease, background-color 180ms ease, color 180ms ease, transform 180ms ease;
}

.run-button {
  border-color: var(--green);
  background: var(--green);
  color: #fff;
}

.program-nonlinear .run-button {
  border-color: var(--orange);
  background: var(--orange);
}

.run-button:hover,
.run-button:focus-visible,
.tool-button:hover,
.tool-button:focus-visible {
  transform: translateY(-1px);
}

.run-button:hover,
.run-button:focus-visible {
  background: #066a4c;
}

.program-nonlinear .run-button:hover,
.program-nonlinear .run-button:focus-visible {
  background: #963b16;
}

.tool-button {
  background: #fff;
}

.tool-button:hover,
.tool-button:focus-visible {
  border-color: #8e8e93;
  background: #f3f3f5;
}

.lab-body {
  display: grid;
  min-height: 510px;
  grid-template-columns: minmax(0, 1fr) 280px;
}

.canvas-wrap {
  position: relative;
  min-width: 0;
  min-height: 510px;
  padding: 18px 18px 52px;
  overflow: hidden;
  border-right: 1px solid var(--line);
  background: #fafafa;
}

.simulation-canvas {
  display: block;
  width: 100%;
  height: 440px;
}

.canvas-legend {
  position: absolute;
  bottom: 17px;
  left: 28px;
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
  color: var(--muted);
  font-size: 13px;
}

.canvas-legend span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.canvas-legend i {
  display: block;
  width: 21px;
  height: 2px;
  background: var(--green);
}

.program-nonlinear .canvas-legend i {
  background: var(--orange);
}

.canvas-legend .legend-exact {
  height: 0;
  border-top: 2px dashed #2c72b8;
  background: transparent;
}

.canvas-legend .legend-initial {
  background: #babac0;
}

.canvas-legend .legend-trail {
  background: #e2a58a;
}

.running-indicator {
  position: absolute;
  top: 26px;
  right: 28px;
  display: inline-flex;
  align-items: center;
  padding: 5px 8px;
  border: 1px solid #d9d9dd;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.88);
  color: var(--muted);
  gap: 6px;
  font-size: 13px;
  backdrop-filter: blur(8px);
}

.running-indicator i {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: #9a9aa0;
}

.simulation-lab.is-running .running-indicator {
  color: var(--green);
}

.program-nonlinear .simulation-lab.is-running .running-indicator {
  color: var(--orange);
}

.simulation-lab.is-running .running-indicator i {
  background: var(--green);
  animation: status-pulse 1.2s ease-in-out infinite;
}

.program-nonlinear .simulation-lab.is-running .running-indicator i {
  background: var(--orange);
}

.lab-controls {
  padding: 28px 22px;
  background: #fff;
}

.lab-controls label {
  display: grid;
  margin-bottom: 27px;
  gap: 10px;
}

.lab-controls label > span {
  display: flex;
  justify-content: space-between;
  font-size: 13px;
  font-weight: 650;
}

.lab-controls output {
  color: var(--green);
  font-variant-numeric: tabular-nums;
}

.program-nonlinear .lab-controls output {
  color: var(--orange);
}

input[type="range"] {
  width: 100%;
  accent-color: var(--green);
  cursor: pointer;
}

.program-nonlinear input[type="range"] {
  accent-color: var(--orange);
}

.live-metrics {
  display: grid;
  margin: 0;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-top: 1px solid var(--line);
  border-left: 1px solid var(--line);
}

.live-metrics div {
  min-width: 0;
  padding: 13px 10px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.live-metrics dt {
  color: var(--muted);
  font-size: 12px;
}

.live-metrics dd {
  margin: 2px 0 0;
  overflow-wrap: anywhere;
  font-size: 16px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.lab-note {
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.code-result-layout {
  display: grid;
  align-items: start;
  margin-top: 64px;
  grid-template-columns: 1fr;
  gap: 24px;
  scroll-margin-top: 82px;
}

.source-block,
.result-block {
  min-width: 0;
  overflow: hidden;
  border: 1px solid #d7d7db;
  border-radius: var(--radius);
  background: var(--surface);
}

.block-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 78px;
  padding: 16px 18px;
  border-bottom: 1px solid var(--line);
  gap: 18px;
}

.block-heading p {
  margin-bottom: 1px;
  font-size: 13px;
}

.block-heading h3 {
  margin: 0;
  font-size: 21px;
}

.source-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 7px;
}

.copy-code,
.source-actions a {
  min-height: 34px;
  padding: 5px 10px;
  background: transparent;
  color: var(--ink);
  font-size: 13px;
}

.copy-code:hover,
.copy-code:focus-visible,
.source-actions a:hover,
.source-actions a:focus-visible {
  border-color: #8e8e93;
  background: #f2f2f4;
}

.code-explorer {
  display: block;
  min-height: 0;
}

.code-viewer {
  height: auto;
  margin: 0;
  padding: 22px 0 28px;
  overflow-x: auto;
  overflow-y: visible;
  color: #242426;
  background: #f7f7f8;
  font-family: Consolas, "SFMono-Regular", monospace;
  font-size: 15px;
  line-height: 1.72;
  tab-size: 4;
}

.code-line {
  display: grid;
  min-width: max-content;
  grid-template-columns: 48px 1fr;
  padding-right: 18px;
  border-left: 3px solid transparent;
  cursor: text;
  transition: background-color 180ms ease, border-color 180ms ease;
}

.code-line:hover {
  background: rgba(0, 0, 0, 0.025);
}

.code-line.formula-line {
  border-left-color: var(--green);
  background: rgba(8, 127, 91, 0.12);
}

.program-nonlinear .code-line.formula-line {
  border-left-color: var(--orange);
  background: rgba(184, 74, 27, 0.13);
}

.code-line.is-selected {
  border-left-color: var(--blue);
  background: #e8f1fb;
}

.code-line.is-grouped {
  background: var(--green-soft);
}

.program-nonlinear .code-line.is-grouped {
  background: var(--orange-soft);
}

.simulation-active .code-line.formula-line {
  animation: code-focus 1.3s ease-in-out infinite;
}

.line-number {
  padding-right: 12px;
  color: #8a8a90;
  text-align: right;
  user-select: none;
}

.line-content {
  white-space: pre;
}

.code-guide {
  height: 720px;
  padding: 22px;
  overflow: auto;
  background: #fff;
}

.guide-heading {
  display: flex;
  align-items: center;
  padding-bottom: 18px;
  border-bottom: 1px solid var(--line);
  gap: 12px;
}

.guide-heading > span {
  color: var(--green);
  font-family: Cambria, Georgia, serif;
  font-size: 34px;
  line-height: 1;
}

.program-nonlinear .guide-heading > span {
  color: var(--orange);
}

.guide-heading b {
  display: block;
  font-size: 18px;
}

.guide-heading p {
  margin: 2px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.guide-groups {
  display: grid;
  padding: 14px 0;
  gap: 5px;
  border-bottom: 1px solid var(--line);
}

.guide-group {
  display: grid;
  align-items: center;
  width: 100%;
  padding: 8px 7px;
  grid-template-columns: max-content 1fr;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
  gap: 16px;
  text-align: left;
  transition: background-color 160ms ease, transform 160ms ease;
}

.guide-group:hover,
.guide-group:focus-visible,
.guide-group.is-active {
  background: var(--green-soft);
  transform: translateX(2px);
}

.program-nonlinear .guide-group:hover,
.program-nonlinear .guide-group:focus-visible,
.program-nonlinear .guide-group.is-active {
  background: var(--orange-soft);
}

.guide-group span {
  color: var(--green);
  font-family: Cambria, Georgia, serif;
  font-size: 18px;
  font-weight: 700;
  white-space: nowrap;
}

.program-nonlinear .guide-group span {
  color: var(--orange);
}

.guide-group b {
  font-size: 14px;
}

.line-explanation {
  padding-top: 19px;
  animation: explanation-in 220ms ease both;
}

.line-explanation > span {
  color: var(--blue);
  font-size: 13px;
  font-weight: 750;
}

.line-explanation h4 {
  margin: 7px 0 7px;
  font-size: 20px;
}

.line-explanation p {
  margin: 0;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.75;
}

.result-gallery {
  display: grid;
  padding: 18px;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}

.result-gallery figure {
  margin: 0;
  overflow: hidden;
  border: 1px solid #e0e0e3;
  border-radius: 6px;
  background: #fff;
  transition: border-color 200ms ease, box-shadow 250ms ease, transform 250ms ease;
}

.result-gallery figure:hover {
  border-color: #b7b7bc;
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.08);
  transform: translateY(-2px);
}

.result-gallery img {
  width: 100%;
  height: auto;
  border-bottom: 1px solid #e6e6e9;
  object-fit: contain;
  background: #fff;
}

.result-gallery figcaption {
  display: grid;
  padding: 12px 14px 14px;
  gap: 2px;
}

.result-gallery figcaption b {
  font-size: 15px;
}

.result-gallery figcaption span {
  color: var(--muted);
  font-size: 14px;
}

.single-result {
  grid-template-columns: 1fr;
  padding-bottom: 24px;
}

.verification-strip {
  display: grid;
  margin: 0 18px 18px;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.verification-strip div {
  min-width: 0;
  padding: 15px 10px;
  border-left: 1px solid var(--line);
}

.verification-strip div:first-child {
  padding-left: 0;
  border-left: 0;
}

.verification-strip span {
  display: block;
  color: var(--muted);
  font-size: 12px;
}

.verification-strip strong {
  display: block;
  margin-top: 3px;
  overflow-wrap: anywhere;
  font-size: 15px;
  font-variant-numeric: tabular-nums;
}

.reading-note {
  margin: 20px 18px 24px;
  padding: 16px;
  border-left: 3px solid var(--orange);
  background: var(--orange-soft);
}

.reading-note h4 {
  margin: 0 0 5px;
  font-size: 14px;
}

.reading-note p {
  margin: 0;
  color: #68564f;
  font-size: 15px;
}

.equation-transition {
  position: relative;
  height: 120svh;
  min-height: 800px;
  background: #171719;
  color: #fff;
}

.transition-sticky {
  position: sticky;
  top: 62px;
  display: flex;
  min-height: calc(100svh - 62px);
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 50px 20px;
  text-align: center;
  opacity: 0.68;
  transform: scale(0.97);
}

.transition-sticky > p {
  margin: 0 0 28px;
  color: #9b9ba1;
  font-size: 16px;
}

.symbol-change {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 36px;
}

.symbol-change span,
.symbol-change strong {
  font-family: Cambria, Georgia, serif;
  font-size: 92px;
  line-height: 1;
}

.symbol-change span {
  color: #7f7f86;
  transform: translateX(calc(var(--transition-progress, 0) * -24px));
}

.symbol-change strong {
  color: #ef8d62;
  transform: translateX(calc((1 - var(--transition-progress, 0)) * 24px));
}

.symbol-change i {
  color: #63d2ad;
  font-size: 44px;
  font-style: normal;
}

.transition-sticky h2 {
  max-width: 760px;
  margin: 32px 0 0;
  font-size: 36px;
  line-height: 1.2;
}

.program-conclusion {
  display: grid;
  margin-top: 54px;
  padding: 28px 0;
  grid-template-columns: 280px minmax(0, 720px);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  gap: 34px;
}

.program-conclusion h3 {
  margin: 0;
  font-size: 19px;
}

.program-conclusion p {
  margin: 0;
  color: var(--muted);
  font-size: 16px;
}

.summary-section {
  padding: 120px 20px;
  background: #e9f3ef;
}

.summary-inner {
  display: grid;
  width: min(100%, var(--max-width));
  margin: 0 auto;
  grid-template-columns: 0.72fr 1.28fr;
  gap: 80px;
}

.summary-title {
  position: sticky;
  top: 105px;
  align-self: start;
}

.summary-title h2,
.reference-inner h2 {
  margin: 0;
  font-size: 44px;
  line-height: 1.14;
}

.learning-list {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid rgba(8, 127, 91, 0.25);
}

.learning-list li {
  display: grid;
  padding: 27px 0;
  grid-template-columns: 52px 1fr;
  border-bottom: 1px solid rgba(8, 127, 91, 0.25);
  gap: 18px;
}

.learning-list > li > span {
  color: var(--green);
  font-size: 13px;
  font-weight: 750;
}

.learning-list h3 {
  margin: 0 0 7px;
  font-size: 20px;
}

.learning-list p {
  margin: 0;
  color: #4d5652;
}

.scope-note {
  grid-column: 2;
  padding: 20px 22px;
  border: 1px solid rgba(8, 127, 91, 0.28);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.50);
}

.scope-note strong {
  color: var(--green);
  font-size: 13px;
}

.scope-note p {
  margin: 6px 0 0;
  color: #4d5652;
}

.reference-section {
  padding: 100px 20px;
  background: var(--surface);
}

.reference-inner {
  display: grid;
  align-items: end;
  width: min(100%, var(--max-width));
  margin: 0 auto;
  grid-template-columns: 0.85fr 1.15fr;
  gap: 70px;
}

.reference-inner > p {
  margin: 0;
  color: var(--muted);
  font-size: 17px;
}

.reference-links {
  display: flex;
  grid-column: 2;
  gap: 24px;
}

.reference-links a {
  color: var(--blue);
  font-weight: 650;
}

.site-footer {
  display: flex;
  justify-content: space-between;
  width: min(calc(100% - 40px), var(--max-width));
  margin: 0 auto;
  padding: 28px 0 34px;
  color: var(--muted);
  font-size: 12px;
}

.site-footer p {
  margin: 0;
}

.toast {
  position: fixed;
  z-index: 300;
  bottom: 24px;
  left: 50%;
  padding: 9px 16px;
  border-radius: 999px;
  background: rgba(29, 29, 31, 0.93);
  color: #fff;
  font-size: 13px;
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 12px);
  transition: opacity 180ms ease, transform 180ms ease;
}

.toast.is-visible {
  opacity: 1;
  transform: translate(-50%, 0);
}

.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 720ms cubic-bezier(0.22, 1, 0.36, 1), transform 720ms cubic-bezier(0.22, 1, 0.36, 1);
}

.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.sequence-reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 620ms cubic-bezier(0.22, 1, 0.36, 1), transform 620ms cubic-bezier(0.22, 1, 0.36, 1);
}

.sequence-reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

@keyframes status-pulse {
  0%, 100% { box-shadow: 0 0 0 0 rgba(8, 127, 91, 0.28); }
  50% { box-shadow: 0 0 0 5px rgba(8, 127, 91, 0); }
}

@keyframes code-focus {
  0%, 100% { background-color: rgba(8, 127, 91, 0.10); }
  50% { background-color: rgba(8, 127, 91, 0.24); }
}

.program-nonlinear .simulation-active .code-line.formula-line {
  animation-name: code-focus-orange;
}

@keyframes code-focus-orange {
  0%, 100% { background-color: rgba(184, 74, 27, 0.11); }
  50% { background-color: rgba(184, 74, 27, 0.25); }
}

@keyframes menu-in {
  from { opacity: 0; transform: translateY(-8px) scale(0.98); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}

@keyframes scroll-dot {
  0%, 100% { opacity: 0.25; transform: translateY(0); }
  50% { opacity: 1; transform: translateY(11px); }
}

@keyframes explanation-in {
  from { opacity: 0; transform: translateY(5px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 1020px) {
  .project-intro h1 {
    font-size: 60px;
  }

  .program-heading {
    grid-template-columns: 150px 1fr;
  }

  .program-heading h2 {
    font-size: 46px;
  }

  .lab-body {
    grid-template-columns: 1fr;
  }

  .canvas-wrap {
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .lab-controls {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0 26px;
  }

  .lab-note {
    align-self: center;
    margin: 0;
  }

  .code-result-layout {
    grid-template-columns: 1fr;
  }

  .code-viewer {
    height: auto;
  }

  .code-explorer {
    grid-template-columns: minmax(0, 1.2fr) minmax(280px, 0.8fr);
  }
}

@media (max-width: 760px) {
  .site-header {
    height: 56px;
  }

  .site-nav {
    width: calc(100% - 28px);
  }

  .nav-links {
    display: none;
  }

  .directory-toggle {
    margin-left: auto;
  }

  .directory-menu {
    top: 50px;
    right: 14px;
    left: 14px;
    width: auto;
  }

  .project-intro {
    height: calc(100svh - 72px);
    min-height: 720px;
    margin-top: 56px;
    background-image: none;
  }

  .project-intro::before {
    background: rgba(248, 248, 250, 0.89);
  }

  .intro-inner {
    min-height: 100%;
    width: calc(100% - 32px);
    padding: 48px 0 36px;
  }

  .project-intro h1 {
    font-size: 44px;
  }

  .intro-copy {
    margin-top: 22px;
    font-size: 17px;
  }

  .intro-facts {
    margin-top: 34px;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    row-gap: 23px;
  }

  .intro-facts div,
  .intro-facts div:first-child {
    padding: 0 13px;
    border-left: 1px solid rgba(0, 0, 0, 0.18);
  }

  .intro-facts div:nth-child(odd) {
    padding-left: 0;
    border-left: 0;
  }

  .program-section {
    padding: 82px 16px 92px;
  }

  .program-heading {
    grid-template-columns: 1fr;
    gap: 23px;
  }

  .step-label {
    padding: 0;
  }

  .program-heading h2 {
    font-size: 36px;
  }

  .program-heading p {
    font-size: 17px;
  }

  .equation-row {
    margin-top: 38px;
    grid-template-columns: 1fr;
  }

  .equation-row > div,
  .equation-row > div:first-child {
    padding: 18px 0;
    border-left: 0;
  }

  .equation-row > div + div {
    border-top: 1px solid var(--line);
  }

  .equation-row strong {
    font-size: 19px;
  }

  .explanation-grid {
    grid-template-columns: 1fr;
  }

  .explanation-grid article,
  .explanation-grid article:first-child {
    padding: 22px 0;
    border-left: 0;
  }

  .explanation-grid article + article {
    border-top: 1px solid var(--line);
  }

  .lab-toolbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .lab-actions {
    width: 100%;
  }

  .run-button,
  .tool-button {
    flex: 1 1 0;
    min-width: 0;
    padding-right: 8px;
    padding-left: 8px;
  }

  .canvas-wrap {
    min-height: 340px;
    padding: 12px 8px 50px;
  }

  .simulation-canvas {
    height: 300px;
  }

  .running-indicator {
    top: 18px;
    right: 14px;
  }

  .canvas-legend {
    right: 10px;
    bottom: 14px;
    left: 14px;
    gap: 9px;
  }

  .lab-controls {
    display: grid;
    padding: 22px 16px;
    grid-template-columns: 1fr;
  }

  .lab-note {
    margin-top: 17px;
  }

  .code-result-layout {
    margin-top: 44px;
  }

  .block-heading {
    align-items: flex-start;
    flex-direction: column;
  }

  .source-actions {
    justify-content: flex-start;
  }

  .code-viewer {
    height: auto;
    border-right: 0;
    border-bottom: 1px solid var(--line);
    font-size: 14px;
  }

  .code-line {
    grid-template-columns: 42px 1fr;
  }

  .code-explorer {
    grid-template-columns: 1fr;
  }

  .code-guide {
    height: auto;
    min-height: 470px;
  }

  .result-gallery,
  .result-gallery:first-child {
    grid-template-columns: 1fr;
    padding: 12px;
  }

  .equation-transition {
    height: 110svh;
    min-height: 680px;
  }

  .transition-sticky {
    top: 56px;
    min-height: calc(100svh - 56px);
  }

  .symbol-change {
    gap: 18px;
  }

  .symbol-change span,
  .symbol-change strong {
    font-size: 54px;
  }

  .symbol-change i {
    font-size: 30px;
  }

  .transition-sticky h2 {
    font-size: 30px;
  }

  .verification-strip {
    margin: 0 12px 14px;
  }

  .verification-strip div {
    padding: 12px 7px;
  }

  .program-conclusion {
    margin-top: 42px;
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .summary-section,
  .reference-section {
    padding: 82px 16px;
  }

  .summary-inner,
  .reference-inner {
    grid-template-columns: 1fr;
    gap: 40px;
  }

  .summary-title {
    position: static;
  }

  .summary-title h2,
  .reference-inner h2 {
    font-size: 36px;
  }

  .scope-note,
  .reference-links {
    grid-column: 1;
  }

  .reference-links {
    flex-direction: column;
    gap: 10px;
  }

  .site-footer {
    display: grid;
    width: calc(100% - 32px);
    gap: 5px;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}