:root {
  --article-frame-gutter: clamp(28px, 3.125vw, 60px);
  --article-inner-gutter: clamp(20px, 2.08vw, 40px);
  --article-frame-width: min(
    calc(100vw - (2 * var(--article-frame-gutter))),
    1800px
  );
  --article-intro-gap: clamp(32px, 2.6vw, 52px);
  --article-intro-top: clamp(48px, 4vw, 56px);
  --article-subtitle-size: clamp(24px, 1.33vw, 25.6px);
  --article-subtitle-line: clamp(28px, 1.6vw, 30.72px);
  --article-body-size: 14.4px;
  --article-body-line: 17.28px;
  --article-chapter-size: clamp(17px, 1.08vw, 20.8px);
  --article-chapter-line: clamp(23px, 1.4vw, 26.88px);
  --article-prose-size: 16px;
  --article-prose-line: 28px;
  --article-prose-width: 620px;
  --article-image-bleed: 80px;
  --article-module-offset: 28px;
  --article-mobile-title-size: var(--article-subtitle-size);
  --article-mobile-title-line: var(--article-subtitle-line);
  --article-mobile-chapter-size: var(--article-chapter-size);
  --article-mobile-chapter-line: var(--article-chapter-line);
}

/* ───────── Canvas & page shell ───────── */

.article-canvas {
  min-height: 100svh;
  padding-bottom: 0;
}

.article-canvas.is-last-chapter {
  min-height: calc(100svh + var(--footer-height));
  padding-bottom: var(--footer-height);
}

.page.page-article {
  min-height: 100svh;
  height: auto;
}

.page-article.is-chapter-transitioning {
  overflow-anchor: none;
}

.page-article .page-main {
  position: relative;
  inset: auto;
  width: 100%;
  height: auto;
  min-height: 0;
  overflow: visible;
  padding: calc(var(--header-height) + var(--article-intro-top)) 0
    clamp(84px, 7vw, 120px);
}

.page-article .page-divider,
.page-article .page-footer {
  display: none;
}

.page-article.is-last-chapter .page-divider,
.page-article.is-last-chapter .page-footer {
  display: block;
}

.page-article.is-last-chapter .page-footer {
  display: block;
}

[hidden] {
  display: none !important;
}

/* ───────── Frame ───────── */

.article-frame {
  width: var(--article-frame-width);
  margin: 0 auto;
  padding-inline: var(--article-inner-gutter);
  overflow: visible;
}

/* ───────── Intro (three columns) ───────── */

.article-intro {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--article-intro-gap);
  width: 100%;
}

.article-column {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  flex: 0 1 auto;
  min-width: 0;
}

.article-column-problem {
  max-width: 320px;
  flex-shrink: 0;
}

.article-column-summary {
  max-width: 400px;
}

.article-column-chapters {
  flex-shrink: 0;
}

/* ── Eyebrow ── */

.article-eyebrow {
  margin: 0;
  color: var(--text-muted);
  font-family: var(--font-code);
  font-size: 13px;
  font-weight: 400;
  line-height: 16px;
  letter-spacing: -0.02em;
  text-transform: none;
}

/* ── Problem column ── */

.article-title {
  margin: var(--article-module-offset) 0 0;
  color: var(--text-main);
  font-family: var(--font-display);
  font-size: var(--article-subtitle-size);
  font-weight: 430;
  line-height: var(--article-subtitle-line);
  letter-spacing: -0.02em;
}

.article-title span,
.article-section-title span {
  display: block;
}

/* ── Jump arrow ── */

.article-jump {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 34px;
  width: auto;
  height: 40px;
  color: var(--text-main);
  text-decoration: none;
}

.article-jump svg {
  flex-shrink: 0;
  transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

.article-jump:focus-visible svg {
  transform: rotate(45deg);
}

.article-jump:focus-visible {
  color: var(--accent);
}

.article-jump:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 4px;
}

.article-jump-label {
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 430;
  letter-spacing: -0.02em;
  color: var(--accent);
  opacity: 0;
  transform: translateX(-4px);
  transition:
    opacity 0.22s ease,
    transform 0.22s ease;
  white-space: nowrap;
  pointer-events: none;
}

.article-jump:focus-visible .article-jump-label {
  opacity: 1;
  transform: translateX(0);
}

@media (hover: hover) and (pointer: fine) {
  .article-jump:hover svg {
    transform: rotate(45deg);
  }

  .article-jump:hover {
    color: var(--accent);
  }

  .article-jump:hover .article-jump-label {
    opacity: 1;
    transform: translateX(0);
  }
}

@media (hover: none), (pointer: coarse) {
  .article-jump svg {
    width: 30px;
    height: 30px;
    transform: rotate(45deg);
  }

  .article-jump:focus-visible svg {
    transform: rotate(45deg);
  }

  .article-jump-label {
    color: currentColor;
    font-size: 15px;
    opacity: 1;
    transform: translateX(0);
  }

  .article-jump:active {
    color: var(--accent);
  }

  .article-jump:active .article-jump-label,
  .article-jump:active .article-jump svg {
    color: var(--accent);
  }
}

/* ── Summary column ── */

.article-summary-block {
  display: grid;
  gap: 22px;
  margin-top: var(--article-module-offset);
}

.page-article.is-chapter-transitioning .article-summary-block {
  overflow-anchor: none;
}

.article-section-title {
  margin: 0;
  color: var(--text-main);
  font-size: var(--article-subtitle-size);
  font-weight: 430;
  line-height: var(--article-subtitle-line);
  letter-spacing: -0.02em;
}

.article-summary {
  max-width: 380px;
  margin: 0;
  color: var(--text-main);
  font-size: var(--article-body-size);
  font-weight: 400;
  line-height: var(--article-body-line);
  letter-spacing: 0;
}

/* ── Chapters column ── */

.article-chapter-list {
  display: grid;
  gap: 3px;
  margin: var(--article-module-offset) 0 0;
  padding: 0;
  list-style: none;
}

.article-chapter-list li {
  margin: 0;
  color: var(--text-main);
  font-size: var(--article-chapter-size);
  font-weight: 430;
  line-height: var(--article-chapter-line);
  letter-spacing: -0.02em;
  transition: color 0.2s ease;
}

.article-chapter-list .is-active {
  color: var(--accent);
}

.article-chapter-list a {
  display: inline-block;
  padding: 1px 0;
  color: inherit;
  text-decoration: none;
  transition: color 0.2s ease;
}

.article-view-toggle-item {
  margin-bottom: 10px;
}

.article-view-toggle {
  display: inline-block;
  padding: 1px 0;
  border: 0;
  background: none;
  color: var(--text-muted);
  font-family: var(--font-code);
  font-size: 13px;
  font-weight: 400;
  line-height: 16px;
  letter-spacing: -0.02em;
  text-align: left;
  cursor: pointer;
  transition: color 0.2s ease;
}

.article-chapter-list li:not(.is-active) a:focus-visible {
  color: var(--accent);
}

.article-chapter-list a:focus-visible,
.article-view-toggle:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 3px;
}

/* ───────── Article body ───────── */

.article-body {
  margin-top: clamp(18px, 2.5vw, 36px);
  overflow: visible;
}

.article-body-rule {
  width: 100%;
  height: 1px;
  background: var(--line);
}

/* ── Chapter blocks — show/hide ── */

.article-prose {
  position: relative;
  width: 100%;
  max-width: var(--article-prose-width);
  margin: 0 auto;
  padding-top: clamp(28px, 3.5vw, 48px);
  overflow: visible;
}

.article-prose-viewport {
  position: relative;
  width: calc(100% + (2 * var(--article-image-bleed)));
  margin-inline: calc(-1 * var(--article-image-bleed));
  padding-inline: var(--article-image-bleed);
  overflow: visible;
}

.page-article.is-chapter-transitioning .article-prose-viewport {
  overflow: clip;
  overflow-anchor: none;
  transition: height var(--chapter-swap-duration) var(--ease-refined);
}

.article-block {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  scroll-margin-top: calc(var(--header-height) + 24px);
  overflow: visible;
}

/* Hidden by default */
.article-block[hidden] {
  display: none;
}

.article-block.is-measuring,
.article-summary-block.is-measuring {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  visibility: hidden;
  pointer-events: none;
}

/* ── Prose content (centered column) ── */

.article-block-content {
  width: 100%;
  max-width: var(--article-prose-width);
  overflow: visible;
  text-wrap: wrap;
}

.article-block-title {
  display: none;
  margin: 0 0 26px;
  color: var(--text-main);
  font-family: var(--font-display);
  font-size: clamp(22px, 1.5vw, 30px);
  font-weight: 430;
  line-height: 1.08;
  letter-spacing: -0.02em;
  text-wrap: wrap;
}

.article-block-content::after {
  content: "";
  display: block;
  clear: both;
}

.article-block-content p {
  margin: 0 0 22px;
  font-size: var(--article-prose-size);
  font-weight: 400;
  line-height: var(--article-prose-line);
  color: var(--text-main);
  letter-spacing: 0;
  text-wrap: wrap;
}

.article-block-content p:last-child {
  margin-bottom: 0;
}

.article-block-content strong {
  font-weight: 600;
}

.article-block-content em {
  font-style: italic;
}

.article-block-content a {
  color: var(--accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.12em;
}

.article-block-content a:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 3px;
}

.article-subheading {
  margin: 0;
  color: var(--text-main);
  font-family: var(--font-display);
  letter-spacing: -0.02em;
  text-wrap: wrap;
}

.article-subheading {
  margin: 8px 0 22px;
  font-size: clamp(21px, 1.34vw, 27px);
  font-weight: 620;
  line-height: 1.22;
  font-style: normal;
  text-decoration: none;
}

.article-subheading-secondary {
  margin: 30px 0 18px;
  font-size: clamp(18px, 1.08vw, 22px);
  font-weight: 500;
  font-style: normal;
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.12em;
}

.article-block-content > * + .article-subheading {
  margin-top: 34px;
}

.article-block-content > * + .article-subheading-secondary {
  margin-top: 30px;
}

/* ── MathJax ── */

.article-block-content .math-block {
  display: block;
  width: 100%;
  margin: 16px 0 18px;
  padding: 0;
  text-align: center;
  overflow-x: auto;
  clear: both;
}

.article-block-content .math-block.math-block-emphasis {
  margin: 22px 0 26px;
  padding: 14px 0;
  border-top: 1px solid rgba(92, 92, 89, 0.3);
  border-bottom: 1px solid rgba(92, 92, 89, 0.3);
}

.article-block-content p + .math-block {
  margin-top: 14px;
}

.article-block-content .math-block + p {
  margin-top: 14px;
}

.article-table-wrap {
  width: 100%;
  margin: 28px 0 30px;
  overflow-x: auto;
}

.article-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 520px;
}

.article-table th,
.article-table td {
  padding: 12px 14px;
  border-top: 1px solid rgba(92, 92, 89, 0.3);
  vertical-align: top;
  text-align: left;
  text-wrap: wrap;
}

.article-table tbody tr:last-child td {
  border-bottom: 1px solid rgba(92, 92, 89, 0.3);
}

.article-table th {
  color: var(--text-muted);
  font-family: var(--font-sans);
  font-size: 12px;
  font-weight: 520;
  line-height: 17px;
  letter-spacing: 0;
  text-transform: none;
}

.article-table td {
  color: var(--text-main);
  font-size: 14px;
  font-weight: 400;
  line-height: 22px;
}

.article-callout {
  margin: 36px 0 10px;
  padding: 18px 20px;
  border: 1px solid rgba(160, 156, 147, 0.24);
  background: rgba(66, 64, 61, 0.92);
  text-align: center;
}

.article-callout p {
  margin: 0;
  font-size: 15px;
  line-height: 24px;
}

.article-list {
  margin: 0 0 26px;
  padding-left: 22px;
}

.article-list li {
  margin: 0 0 16px;
  color: var(--text-main);
  font-size: var(--article-prose-size);
  font-weight: 400;
  line-height: var(--article-prose-line);
  text-wrap: wrap;
}

.article-list ul {
  margin: 14px 0 0;
  padding-left: 22px;
}

.article-list ul li {
  margin-bottom: 10px;
}

/* ───────── Article images ───────── */

/* ── Centered image (slightly wider than prose column) ── */
.article-image,
.article-image-left,
.article-image-right {
  align-self: center;
  width: calc(100% + (2 * var(--article-image-bleed)));
  margin: 36px calc(-1 * var(--article-image-bleed));
}

.article-image img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

.article-image-caption {
  margin: 10px 0 0;
  padding: 0 var(--article-image-bleed);
  font-family: var(--font-code);
  font-size: 12px;
  font-weight: 400;
  line-height: 16px;
  color: var(--text-muted);
  letter-spacing: 0;
}

.article-image-left img,
.article-image-right img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

.article-image-left .article-image-caption,
.article-image-right .article-image-caption {
  padding: 0 var(--article-image-bleed);
  text-align: left;
}

/* ───────── Chapter navigator ───────── */

.chapter-nav {
  width: 100%;
  margin-top: clamp(56px, 5vw, 88px);
  --chapter-nav-rule-width: 280px;
}

.chapter-nav-inner {
  display: flex;
  align-items: center;
  justify-content: center;
  max-width: var(--article-frame-width);
  margin: 0 auto;
  padding: 0 20px;
}

/* ── Center (copy + lines) ── */

.chapter-nav-center {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 10px;
  width: 100%;
  padding: 14px 0 12px;
  min-width: 0;
}

.chapter-nav-center::before,
.chapter-nav-center::after {
  content: "";
  width: 100%;
  height: 1px;
  background: var(--line);
  flex: 0 0 auto;
}

.chapter-nav-continue {
  margin: 0;
  padding: 10px 16px;
  background: none;
  border: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 40px;
  max-width: 100%;
  font-family: var(--font-display);
  font-size: 15px;
  font-weight: 400;
  line-height: 18px;
  color: var(--text-main);
  letter-spacing: -0.02em;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  cursor: pointer;
  position: relative;
  z-index: 1;
  transition: color 0.2s ease, opacity 0.2s ease;
}

.chapter-nav-continue-text {
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
}

.chapter-nav-continue-icon {
  display: block;
  width: 14px;
  height: 14px;
  flex: 0 0 auto;
  opacity: 0.7;
  transform: translate(0, 0.5px);
  transition: transform 0.2s ease, opacity 0.2s ease;
}

.chapter-nav-continue:focus-visible {
  color: var(--accent);
}

.chapter-nav-continue:focus-visible .chapter-nav-continue-icon {
  opacity: 1;
  transform: translate(1px, 0.5px);
}

.chapter-nav-continue:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 6px;
}

.chapter-nav-continue:disabled {
  cursor: default;
  opacity: 0.65;
  pointer-events: none;
}

/* ───────── Feature (next problem) ───────── */

.article-feature {
  display: grid;
  gap: 24px;
  width: 100%;
  margin-top: clamp(80px, 7vw, 128px);
  scroll-margin-top: calc(var(--header-height) + 24px);
}

.article-feature-title {
  margin: 0;
  color: var(--text-main);
  font-family: var(--font-display);
  font-size: 51px;
  font-weight: 540;
  line-height: 51px;
  letter-spacing: -1.024px;
}

.article-feature-card {
  display: grid;
  gap: 16px;
  width: min(100%, 546px);
  color: inherit;
  text-decoration: none;
}

.article-feature-preview {
  position: relative;
  overflow: hidden;
  width: min(100%, 526px);
  aspect-ratio: 526 / 336;
  background: rgba(238, 237, 228, 0.5);
}

.article-feature-preview img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center 54%;
  transform: scale(1.03);
  transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.article-feature-card:focus-visible .article-feature-preview img {
  transform: scale(1.07);
}

.article-feature-meta {
  display: flex;
  align-items: flex-end;
  gap: 12px;
  min-height: 31px;
}

.article-feature-link {
  color: var(--text-main);
  font-size: var(--article-subtitle-size);
  font-weight: 430;
  line-height: var(--article-subtitle-line);
  letter-spacing: -0.02em;
}

.article-feature-kicker {
  padding-bottom: 2px;
  color: var(--text-muted);
  font-family: var(--font-code);
  font-size: 11px;
  font-weight: 400;
  line-height: 14px;
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.article-feature-card:focus-visible .article-feature-link {
  color: var(--accent);
}

.article-feature-card:focus-visible .article-feature-kicker {
  color: var(--accent-muted);
}

.article-feature-card:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 6px;
}

.page-article.is-full-view .article-block {
  align-items: stretch;
}

.page-article.is-full-view .article-block + .article-block {
  margin-top: clamp(52px, 5vw, 88px);
  padding-top: clamp(28px, 3vw, 40px);
  border-top: 1px solid var(--line);
}

.page-article.is-full-view .article-block-title {
  display: block;
  margin: 0 0 30px;
  color: var(--accent);
  font-size: clamp(26px, 1.7vw, 34px);
  font-weight: 700;
  line-height: 1.05;
}

.page-article.is-full-view .chapter-nav {
  display: none;
}

@media (hover: hover) and (pointer: fine) {
  .article-chapter-list li:not(.is-active) a:hover {
    color: var(--accent);
  }

  .chapter-nav-continue:hover {
    color: var(--accent);
  }

  .chapter-nav-continue:hover .chapter-nav-continue-icon {
    opacity: 1;
    transform: translate(1px, 0.5px);
  }

  .article-feature-card:hover .article-feature-preview img {
    transform: scale(1.07);
  }

  .article-feature-card:hover .article-feature-link {
    color: var(--accent);
  }

  .article-feature-card:hover .article-feature-kicker {
    color: var(--accent-muted);
  }

  .article-view-toggle:hover {
    color: var(--accent);
  }
}

@media (hover: none), (pointer: coarse) {
  .article-chapter-list li:not(.is-active) a:active {
    color: var(--accent);
  }

  .chapter-nav-continue:active {
    color: var(--accent);
  }

  .chapter-nav-continue:active .chapter-nav-continue-icon {
    opacity: 1;
    transform: translate(1px, 0.5px);
  }

  .article-feature-card:active .article-feature-preview img {
    transform: scale(1.07);
  }

  .article-feature-card:active .article-feature-link {
    color: var(--accent);
  }

  .article-feature-card:active .article-feature-kicker {
    color: var(--accent-muted);
  }

  .article-view-toggle:active {
    color: var(--accent);
  }
}

/* ───────── Transition for chapter swap ───────── */

.article-block {
  animation: chapterIn 0.24s var(--ease-gentle) both;
}

.article-block[data-suppress-intro="true"] {
  animation: none;
}

.page-article.is-chapter-transitioning .article-block {
  animation: none;
}

.page-article.is-chapter-transitioning .article-block-content {
  animation: chapterSubtleReveal 0.4s var(--ease-gentle) both;
}

@keyframes chapterIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes chapterSubtleReveal {
  from {
    opacity: 0.08;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ───────── Breakpoints ───────── */

@media (max-width: 1279.98px) {
  .article-intro {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    gap: 48px 32px;
  }

  .article-column {
    width: 100%;
    max-width: none;
    flex: none;
  }

  .article-column-problem {
    max-width: none;
  }

  .article-column-chapters {
    grid-column: 1 / -1;
  }

  .article-summary {
    max-width: 38ch;
  }
}

@media (max-width: 809.98px) {
  :root {
    --article-frame-gutter: 22px;
    --article-inner-gutter: 0px;
    --article-intro-top: 28px;
    --article-image-bleed: 16px;
    --article-mobile-title-size: 22px;
    --article-mobile-title-line: 27px;
    --article-mobile-chapter-size: 18px;
    --article-mobile-chapter-line: 24px;
  }

  .page-article .page-main {
    padding-bottom: 72px;
  }

  .article-intro {
    grid-template-columns: 1fr;
    gap: 36px;
  }

  .article-title,
  .article-section-title,
  .article-feature-link {
    font-size: 22px;
    line-height: 27px;
  }

  .article-jump {
    margin-top: 28px;
  }

  .article-jump-label {
    font-size: 18px;
  }

  .article-summary-block {
    gap: 18px;
  }

  .article-view-toggle {
    font-size: 12px;
    line-height: 16px;
  }

  .article-chapter-list li {
    font-size: 18px;
    line-height: 24px;
  }

  .article-block-content {
    max-width: none;
  }

  .article-block-content p {
    font-size: 14.5px;
    line-height: 24px;
  }

  .article-block-title {
    margin-bottom: 20px;
    font-size: 22px;
    line-height: 27px;
  }

  .page-article.is-full-view .article-block-title {
    margin-bottom: 24px;
    font-size: 24px;
    line-height: 28px;
  }

  .article-subheading {
    margin-bottom: 20px;
    font-size: 19px;
    line-height: 24px;
  }

  .article-subheading-secondary {
    margin: 24px 0 16px;
    font-size: 17px;
    line-height: 22px;
  }

  .article-block-content p {
    margin-bottom: 20px;
  }

  .article-block-content > * + .article-subheading {
    margin-top: 28px;
  }

  .article-block-content .math-block {
    margin: 14px 0 16px;
  }

  .article-block-content .math-block.math-block-emphasis {
    margin: 18px 0 22px;
  }

  .article-image {
    width: 100%;
    margin: 28px 0;
  }

  .article-image-caption {
    padding: 0;
  }

  .article-image-left,
  .article-image-right {
    width: 100%;
    margin: 28px 0;
  }

  .article-image-left .article-image-caption,
  .article-image-right .article-image-caption {
    padding: 10px 0 0 0;
    text-align: left;
  }

  .article-feature {
    gap: 20px;
    margin-top: 64px;
  }

  .article-feature-title {
    font-size: 40px;
    line-height: 40px;
    letter-spacing: -0.8px;
  }

  .article-feature-card,
  .article-feature-preview {
    width: 100%;
  }

  .article-table th,
  .article-table td {
    padding: 10px 12px;
  }

  .article-table td {
    font-size: 13px;
    line-height: 20px;
  }

  .article-callout {
    margin: 30px 0 8px;
    padding: 16px 14px;
  }

  .article-callout p {
    font-size: 14px;
    line-height: 22px;
  }

  .article-list li {
    margin-bottom: 14px;
    font-size: 14.5px;
    line-height: 24px;
  }

  .article-feature-meta {
    flex-direction: column;
    align-items: flex-start;
    gap: 6px;
  }

  .chapter-nav-inner {
    padding: 0 14px;
  }

  .chapter-nav-center {
    gap: 8px;
    padding: 12px 0 10px;
  }

  .chapter-nav-continue {
    font-size: 12px;
    line-height: 14px;
  }

  .chapter-nav-continue-icon {
    width: 12px;
    height: 12px;
  }
}

@media (max-width: 960px) {
  .page-article .menu-right,
  .page-article .article-mobile-drawer .drawer-meta {
    display: none;
  }

  .page-article.is-mobile-chapter-menu .article-intro {
    display: grid;
    grid-template-columns: minmax(0, 1fr);
    gap: 0;
  }

  .page-article.is-mobile-chapter-menu .article-column-problem,
  .page-article.is-mobile-chapter-menu .article-column-chapters {
    display: none;
  }

  .page-article.is-mobile-chapter-menu .article-column-summary {
    width: 100%;
    max-width: none;
  }

  .page-article.is-mobile-chapter-menu .article-summary-block,
  .page-article.is-mobile-chapter-menu .article-summary {
    max-width: none;
  }

  .article-drawer-panel {
    height: auto;
    min-height: 0;
    max-height: min(85svh, 720px);
    justify-content: flex-start;
    padding: calc(var(--header-height) + var(--article-intro-top)) 0 24px;
    overflow-y: auto;
  }

  .article-drawer-content {
    display: grid;
    gap: var(--article-intro-gap);
    width: var(--article-frame-width);
    margin: 0 auto;
    padding-inline: var(--article-inner-gutter);
  }

  .article-drawer-block {
    display: grid;
    gap: 0;
  }

  .article-drawer-problem {
    max-width: 320px;
  }

  .article-drawer-toc {
    max-width: 360px;
  }

  .article-drawer-title {
    margin-top: var(--article-module-offset);
    font-size: var(--article-mobile-title-size);
    line-height: var(--article-mobile-title-line);
  }

  .article-drawer-problem .article-jump {
    margin-top: 28px;
  }

  .article-drawer-chapter-list {
    gap: 3px;
    margin-top: var(--article-module-offset);
  }

  .article-drawer-chapter-list li {
    font-size: var(--article-mobile-chapter-size);
    line-height: var(--article-mobile-chapter-line);
    letter-spacing: -0.02em;
  }

  .article-drawer-chapter-list a {
    display: inline-block;
    padding: 1px 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  .article-block {
    animation: none;
  }

  .page-article.is-chapter-transitioning .article-prose-viewport,
  .page-article.is-chapter-transitioning .article-summary-block {
    transition: none;
  }
}