@import url("https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;700&family=IBM+Plex+Serif:wght@400;600&display=swap");

:root {
  --bg: #e8eef2;
  --panel: #f7fbff;
  --panel-2: #eef6fc;
  --ink: #0f1a24;
  --muted: #445463;
  --line: #bfd0df;
  --brand: #0f6e8a;
  --brand-deep: #0b566d;
  --accent: #1d8fb4;
  --accent-soft: #dff2fa;
  --shadow: 0 20px 50px rgba(11, 26, 38, 0.1);
  --radius: 18px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Space Grotesk", sans-serif;
  color: var(--ink);
  background:
    linear-gradient(rgba(15, 110, 138, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(15, 110, 138, 0.06) 1px, transparent 1px),
    radial-gradient(circle at 12% 8%, rgba(29, 143, 180, 0.14), transparent 42%),
    radial-gradient(circle at 88% 12%, rgba(16, 120, 168, 0.08), transparent 46%),
    linear-gradient(180deg, #e3ebf1 0%, var(--bg) 30%, #edf3f7 100%);
  background-size: 24px 24px, 24px 24px, auto, auto, auto;
  line-height: 1.5;
}

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

a {
  color: var(--brand-deep);
}

a:hover,
a:focus-visible {
  color: var(--brand);
}

.skip-link {
  position: absolute;
  left: 0.75rem;
  top: -3rem;
  background: var(--ink);
  color: #fff;
  padding: 0.6rem 0.9rem;
  border-radius: 10px;
  z-index: 999;
}

.skip-link:focus {
  top: 0.75rem;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.header-shell,
.section-shell {
  width: min(1120px, calc(100% - 2rem));
  margin-inline: auto;
}

.site-header {
  padding-top: 1rem;
}

.header-shell {
  display: grid;
  grid-template-columns: 1.25fr 0.75fr;
  gap: 1rem;
  align-items: stretch;
  margin-top: 1rem;
}

.brand-block,
.hero-panel {
  background: rgba(247, 251, 255, 0.85);
  border: 1px solid rgba(191, 208, 223, 0.9);
  border-radius: calc(var(--radius) + 6px);
  box-shadow: var(--shadow);
  backdrop-filter: blur(10px);
}

.brand-block {
  padding: 1.2rem 1.2rem 1.4rem;
  position: relative;
  overflow: clip;
}

.brand-block::after {
  content: "";
  position: absolute;
  inset: auto -10% -30% auto;
  width: 280px;
  height: 280px;
  background:
    radial-gradient(circle, rgba(15, 110, 138, 0.2) 0 2px, transparent 3px),
    repeating-radial-gradient(circle, rgba(15, 110, 138, 0.14) 0 1px, transparent 1px 9px);
  opacity: 0.55;
  pointer-events: none;
}

.eyebrow {
  margin: 0 0 0.35rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 0.78rem;
  color: var(--brand-deep);
  font-weight: 700;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.brand-block h1 {
  margin: 0;
  font-size: clamp(2rem, 3vw + 1rem, 3.6rem);
  line-height: 1.05;
  max-width: 16ch;
  font-family: "IBM Plex Serif", serif;
}

.lede {
  margin: 0.9rem 0 0;
  max-width: 55ch;
  color: var(--muted);
  font-size: 1.05rem;
}

.hero-actions {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-top: 1.1rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 999px;
  padding: 0.75rem 1rem;
  font-weight: 700;
  text-decoration: none;
  border: 1px solid transparent;
  transition: transform 140ms ease, box-shadow 140ms ease, background-color 140ms ease;
}

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

.btn-primary {
  background: var(--brand);
  color: #fff;
  box-shadow: 0 8px 20px rgba(15, 118, 110, 0.25);
}

.btn-primary:hover,
.btn-primary:focus-visible {
  color: #fff;
  background: #0b6a63;
}

.btn-secondary {
  background: #fff;
  border-color: var(--line);
}

.hero-panel {
  padding: 1rem 1.1rem;
  align-self: start;
}

.hero-panel h2 {
  margin: 0;
  font-size: 1.2rem;
}

.hero-panel ol {
  margin: 0.75rem 0 0;
  padding-left: 1.15rem;
  color: var(--muted);
}

.hero-panel li + li {
  margin-top: 0.45rem;
}

.panel-note {
  margin: 0.9rem 0 0;
  font-size: 0.93rem;
  color: var(--muted);
  border-top: 1px solid var(--line);
  padding-top: 0.75rem;
}

.site-nav {
  width: min(1120px, calc(100% - 2rem));
  margin: 0.8rem auto 0;
  background: rgba(248, 252, 255, 0.86);
  border: 1px solid rgba(191, 208, 223, 0.9);
  border-radius: 14px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(8px);
}

.site-nav ul {
  margin: 0;
  padding: 0.6rem;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.site-nav a {
  display: inline-block;
  text-decoration: none;
  padding: 0.55rem 0.85rem;
  border-radius: 10px;
  color: var(--ink);
  font-weight: 500;
  border: 1px solid transparent;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  background: rgba(15, 110, 138, 0.08);
  border-color: rgba(15, 110, 138, 0.15);
  color: var(--brand-deep);
}

.search-strip {
  margin-top: 1rem;
}

.search-strip .section-shell {
  background:
    linear-gradient(rgba(255, 255, 255, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.05) 1px, transparent 1px),
    linear-gradient(135deg, rgba(10, 79, 103, 0.97), rgba(11, 104, 132, 0.97));
  background-size: 18px 18px, 18px 18px, auto;
  color: #fff;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1rem;
  display: grid;
  gap: 0.8rem;
  align-items: center;
}

.search-strip h2 {
  margin: 0.2rem 0 0;
  font-size: clamp(1.3rem, 2vw + 0.5rem, 2rem);
}

.search-strip .eyebrow {
  color: rgba(255, 255, 255, 0.86);
}

.search-box input {
  width: 100%;
  border-radius: 14px;
  border: 1px solid rgba(255, 255, 255, 0.32);
  background: rgba(255, 255, 255, 0.13);
  color: #fff;
  padding: 0.95rem 1rem;
  font: inherit;
}

.search-box input::placeholder {
  color: rgba(255, 255, 255, 0.72);
}

.search-box input:focus-visible {
  outline: 3px solid rgba(255, 255, 255, 0.5);
  outline-offset: 2px;
}

.section {
  padding: 1.2rem 0 0.3rem;
}

.section-alt .section-shell {
  background: rgba(255, 253, 248, 0.7);
  border: 1px solid rgba(213, 201, 183, 0.75);
  border-radius: var(--radius);
  padding: 1rem;
  box-shadow: var(--shadow);
}

.section-heading h2 {
  margin: 0;
  font-size: clamp(1.4rem, 1.7vw + 0.8rem, 2.25rem);
  font-family: "IBM Plex Serif", serif;
}

.section-heading p:last-child {
  margin: 0.4rem 0 0;
  color: var(--muted);
  max-width: 65ch;
}

.section-heading-row {
  display: flex;
  gap: 1rem;
  justify-content: space-between;
  align-items: end;
  flex-wrap: wrap;
}
.path-grid,
.fundamental-grid,
.tutorial-grid,
.technique-grid {
  display: grid;
  gap: 0.9rem;
  margin-top: 0.9rem;
}

.path-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.path-card,
.topic-card,
.tutorial-card,
.technique-card,
.glossary-item {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 0.95rem;
  box-shadow: 0 10px 28px rgba(23, 33, 38, 0.07);
  transition: transform 160ms ease, box-shadow 160ms ease, opacity 140ms ease;
  position: relative;
  overflow: hidden;
}

.path-card::before,
.topic-card::before,
.tutorial-card::before,
.technique-card::before,
.glossary-item::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(180deg, rgba(15, 110, 138, 0.03), transparent 45%),
    linear-gradient(90deg, rgba(15, 110, 138, 0.025) 1px, transparent 1px);
  background-size: auto, 14px 14px;
  pointer-events: none;
}

.path-card:hover,
.topic-card:hover,
.tutorial-card:hover,
.technique-card:hover,
.glossary-item:hover {
  transform: translateY(-2px);
  box-shadow: 0 14px 34px rgba(23, 33, 38, 0.1);
}

.path-card h3,
.topic-card h3,
.tutorial-card h3,
.technique-card h3,
.glossary-item h3 {
  margin: 0;
  font-size: 1.06rem;
}

.path-card p,
.topic-card p,
.tutorial-card p,
.technique-card p,
.glossary-item p {
  margin: 0.45rem 0 0;
  color: var(--muted);
}

.topic-card p,
.glossary-item p {
  line-height: 1.45;
}

.path-card ul,
.tutorial-card ul {
  margin: 0.65rem 0 0;
  padding-left: 1rem;
}

.path-card li + li,
.tutorial-card li + li {
  margin-top: 0.2rem;
}

.path-card a {
  display: inline-block;
  margin-top: 0.75rem;
  font-weight: 700;
}

.path-card[data-level="beginner"] {
  border-top: 5px solid #0f766e;
}

.path-card[data-level="intermediate"] {
  border-top: 5px solid #d97706;
}

.path-card[data-level="expert"] {
  border-top: 5px solid #9a3412;
}

.fundamental-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.tutorial-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.card-level {
  margin: 0;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--brand-deep);
  font-weight: 700;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.filter-group {
  display: flex;
  gap: 0.45rem;
  flex-wrap: wrap;
}

.filter-btn {
  border: 1px solid var(--line);
  background: #f8fcff;
  color: var(--ink);
  font: inherit;
  border-radius: 999px;
  padding: 0.55rem 0.75rem;
  cursor: pointer;
  transition: background-color 140ms ease, color 140ms ease, border-color 140ms ease;
}

.filter-btn:hover,
.filter-btn:focus-visible {
  border-color: var(--brand);
}

.filter-btn.is-active {
  background: var(--accent-soft);
  border-color: rgba(29, 143, 180, 0.45);
  color: #0b566d;
}

.results-note {
  min-height: 1.25rem;
  margin-top: 0.65rem;
  color: var(--muted);
}

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

.technique-card {
  background:
    linear-gradient(180deg, rgba(15, 110, 138, 0.05), transparent 60%),
    linear-gradient(180deg, var(--panel-2), var(--panel));
}

.accordion {
  margin-top: 0.85rem;
  display: grid;
  gap: 0.65rem;
}

.accordion-item {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 0.1rem 0.9rem;
  box-shadow: 0 8px 20px rgba(23, 33, 38, 0.06);
  position: relative;
}

.accordion-item::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 3px;
  background: linear-gradient(90deg, rgba(15, 110, 138, 0.65), rgba(29, 143, 180, 0.35));
  border-radius: 14px 14px 0 0;
  pointer-events: none;
}

.accordion-item summary {
  cursor: pointer;
  padding: 0.85rem 1.6rem 0.85rem 0;
  font-weight: 600;
  list-style: none;
  position: relative;
}

.accordion-item summary::-webkit-details-marker {
  display: none;
}

.accordion-item summary::after {
  content: "+";
  position: absolute;
  right: 0;
  top: 50%;
  transform: translateY(-50%);
  color: var(--brand-deep);
  font-size: 1.2rem;
}

.accordion-item[open] summary::after {
  content: "-";
}

.accordion-content {
  padding: 0 0 0.85rem;
  color: var(--muted);
}

.accordion-content p {
  margin: 0;
}

.accordion-content ul {
  margin: 0.55rem 0 0;
  padding-left: 1rem;
}

.accordion-content li + li {
  margin-top: 0.25rem;
}

.glossary-list {
  margin-top: 0.9rem;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.8rem;
}

.site-footer {
  padding: 1.3rem 0 1.8rem;
}

.footer-shell {
  border-top: 1px solid rgba(213, 201, 183, 0.8);
  padding-top: 1rem;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.footer-shell p {
  margin: 0;
  color: var(--muted);
}

.footer-links {
  display: flex;
  gap: 1rem;
  align-items: center;
  flex-wrap: wrap;
}

.footer-links a {
  text-decoration: none;
  font-weight: 600;
}

.card-link {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-weight: 700;
}

.card-link::after {
  content: "->";
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
}

.is-hidden {
  display: none !important;
}

.is-faded {
  opacity: 0.45;
}

.search-match {
  outline: 2px solid rgba(15, 118, 110, 0.22);
}

.article-page {
  background:
    linear-gradient(rgba(15, 110, 138, 0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(15, 110, 138, 0.045) 1px, transparent 1px),
    radial-gradient(circle at 8% 6%, rgba(29, 143, 180, 0.12), transparent 42%),
    linear-gradient(180deg, #e5edf3 0%, #eef4f8 32%, #e8eff4 100%);
  background-size: 20px 20px, 20px 20px, auto, auto;
}

.article-header-shell {
  width: min(1200px, calc(100% - 2rem));
  margin-inline: auto;
  margin-top: 1rem;
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 1rem;
}

.article-hero,
.article-meta-panel {
  background: rgba(247, 251, 255, 0.9);
  border: 1px solid rgba(191, 208, 223, 0.95);
  border-radius: 18px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(10px);
}

.article-hero {
  padding: 1rem 1.1rem 1.15rem;
  position: relative;
  overflow: clip;
}

.article-hero::after {
  content: "";
  position: absolute;
  right: -6%;
  bottom: -18%;
  width: 340px;
  height: 220px;
  opacity: 0.45;
  background:
    linear-gradient(90deg, rgba(15, 110, 138, 0.14) 1px, transparent 1px),
    linear-gradient(0deg, rgba(15, 110, 138, 0.08) 1px, transparent 1px),
    linear-gradient(180deg, rgba(29, 143, 180, 0.12), transparent 60%);
  background-size: 18px 18px, 18px 18px, auto;
  pointer-events: none;
}

.article-breadcrumb {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  text-decoration: none;
  font-weight: 700;
  margin-bottom: 0.6rem;
}

.article-breadcrumb::before {
  content: "<-";
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.article-hero h1 {
  margin: 0;
  font-family: "IBM Plex Serif", serif;
  font-size: clamp(1.85rem, 2.1vw + 1rem, 3rem);
  line-height: 1.05;
  max-width: 22ch;
}

.article-lede {
  margin: 0.7rem 0 0;
  color: var(--muted);
  max-width: 72ch;
}

.article-keywords {
  margin: 0.9rem 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.keyword-chip {
  display: inline-flex;
  align-items: center;
  border: 1px solid rgba(15, 110, 138, 0.18);
  background: rgba(15, 110, 138, 0.06);
  border-radius: 999px;
  padding: 0.35rem 0.6rem;
  font-size: 0.82rem;
}

.article-meta-panel {
  padding: 0.95rem 1rem;
}

.article-meta-panel h2 {
  margin: 0;
  font-size: 1.05rem;
  font-family: "IBM Plex Serif", serif;
}

.article-meta-panel ul {
  margin: 0.65rem 0 0;
  padding-left: 1rem;
  color: var(--muted);
}

.article-meta-panel li + li {
  margin-top: 0.25rem;
}

.article-main-shell {
  width: min(1200px, calc(100% - 2rem));
  margin: 1rem auto 0;
}

.article-layout {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 1rem;
  align-items: start;
}

.article-toc {
  position: sticky;
  top: 1rem;
  background: rgba(247, 251, 255, 0.9);
  border: 1px solid rgba(191, 208, 223, 0.9);
  border-radius: 16px;
  box-shadow: 0 12px 28px rgba(11, 26, 38, 0.07);
  padding: 0.85rem;
}

.article-toc h2 {
  margin: 0;
  font-size: 1rem;
  font-family: "IBM Plex Serif", serif;
}

.article-toc ol {
  margin: 0.65rem 0 0;
  padding-left: 1rem;
}

.article-toc li + li {
  margin-top: 0.28rem;
}

.article-toc a {
  text-decoration: none;
  color: var(--muted);
}

.article-toc a:hover,
.article-toc a:focus-visible {
  color: var(--brand-deep);
}

.article-content {
  display: grid;
  gap: 0.95rem;
}

.article-panel {
  background: rgba(247, 251, 255, 0.92);
  border: 1px solid rgba(191, 208, 223, 0.92);
  border-radius: 16px;
  box-shadow: 0 12px 28px rgba(11, 26, 38, 0.07);
  padding: 0.95rem 1rem;
}

.article-panel h2 {
  margin: 0;
  font-family: "IBM Plex Serif", serif;
  font-size: 1.35rem;
}

.article-panel h3 {
  margin: 0.85rem 0 0;
  font-size: 1rem;
  font-family: "IBM Plex Serif", serif;
}

.article-panel p {
  margin: 0.55rem 0 0;
  color: var(--muted);
}

.article-panel ul,
.article-panel ol {
  margin: 0.55rem 0 0;
  padding-left: 1.05rem;
  color: var(--muted);
}

.article-panel li + li {
  margin-top: 0.28rem;
}

.eq-block {
  margin-top: 0.75rem;
  background:
    linear-gradient(180deg, rgba(15, 110, 138, 0.04), rgba(15, 110, 138, 0.015)),
    rgba(255, 255, 255, 0.8);
  border: 1px solid rgba(191, 208, 223, 0.9);
  border-radius: 12px;
  padding: 0.7rem 0.8rem;
}

.eq-block code,
.eq-block pre {
  margin: 0;
  display: block;
  overflow-x: auto;
  white-space: pre;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9rem;
  line-height: 1.45;
  color: #113040;
}

.eq-block pre {
  background: transparent;
}

.eq-block .katex-display {
  margin: 0;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.1rem 0;
}

.eq-block .katex-display > .katex {
  text-align: left;
}

.eq-block .katex {
  font-size: 1em;
}

.eq-block .katex-error {
  color: #8b1e1e;
  white-space: pre-wrap;
  word-break: break-word;
}

.eq-note {
  margin-top: 0.45rem;
  font-size: 0.9rem;
  color: var(--muted);
}

.note-callout {
  margin-top: 0.75rem;
  border-left: 4px solid rgba(15, 110, 138, 0.55);
  background: rgba(15, 110, 138, 0.045);
  padding: 0.65rem 0.75rem;
  border-radius: 0 10px 10px 0;
}

.note-callout p {
  margin: 0;
}

.subgrid-2 {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
  margin-top: 0.75rem;
}

.mini-panel {
  border: 1px solid rgba(191, 208, 223, 0.85);
  background: rgba(255, 255, 255, 0.72);
  border-radius: 12px;
  padding: 0.7rem;
}

.mini-panel h3 {
  margin: 0;
  font-size: 0.98rem;
}

.mini-panel p {
  margin: 0.45rem 0 0;
  font-size: 0.95rem;
}

.math-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 0.75rem;
  font-size: 0.95rem;
}

.math-table th,
.math-table td {
  text-align: left;
  padding: 0.55rem 0.6rem;
  border-bottom: 1px solid rgba(191, 208, 223, 0.75);
  vertical-align: top;
}

.math-table th {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.85rem;
  color: var(--brand-deep);
  letter-spacing: 0.04em;
}

.math-table td code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
}

.diagram-grid {
  margin-top: 0.75rem;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
}

.diagram-box {
  background: rgba(255, 255, 255, 0.78);
  border: 1px solid rgba(191, 208, 223, 0.85);
  border-radius: 12px;
  padding: 0.7rem;
}

.diagram-box h3 {
  margin: 0;
  font-size: 0.95rem;
}

.diagram-box svg {
  width: 100%;
  height: auto;
  display: block;
  margin-top: 0.55rem;
  border-radius: 8px;
  background: #f7fbff;
  border: 1px solid rgba(191, 208, 223, 0.75);
}

.diagram-box img {
  width: 100%;
  height: auto;
  display: block;
  margin-top: 0.55rem;
  border-radius: 8px;
  background: #f7fbff;
  border: 1px solid rgba(191, 208, 223, 0.75);
}

.diagram-box p {
  margin: 0.45rem 0 0;
  font-size: 0.93rem;
}

.notation-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.55rem 0.85rem;
  margin-top: 0.75rem;
}

.notation-list div {
  border-top: 1px solid rgba(191, 208, 223, 0.75);
  padding-top: 0.45rem;
}

.notation-list dt {
  margin: 0;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color: var(--brand-deep);
  font-weight: 700;
}

.notation-list dd {
  margin: 0.25rem 0 0;
  color: var(--muted);
}

.article-footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 0.85rem;
}

.article-footer-nav a {
  display: inline-flex;
  align-items: center;
  border: 1px solid rgba(15, 110, 138, 0.18);
  background: rgba(15, 110, 138, 0.05);
  border-radius: 999px;
  padding: 0.45rem 0.7rem;
  text-decoration: none;
  font-weight: 600;
}

.article-page .site-footer {
  padding-top: 1rem;
}

.article-page .footer-shell {
  border-top-color: rgba(191, 208, 223, 0.85);
}

.tool-layout {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 0.9rem;
  align-items: start;
}

.tool-controls {
  background: rgba(255, 255, 255, 0.78);
  border: 1px solid rgba(191, 208, 223, 0.85);
  border-radius: 14px;
  padding: 0.8rem;
}

.tool-controls h3 {
  margin: 0;
  font-family: "IBM Plex Serif", serif;
  font-size: 1rem;
}

.control-stack {
  display: grid;
  gap: 0.8rem;
  margin-top: 0.65rem;
}

.control-row {
  display: grid;
  gap: 0.35rem;
}

.control-row label,
.control-group-label {
  font-weight: 600;
  color: var(--ink);
}

.control-row input[type="range"] {
  width: 100%;
  accent-color: var(--brand);
}

.control-inline {
  display: flex;
  justify-content: space-between;
  gap: 0.6rem;
  align-items: center;
  font-size: 0.92rem;
  color: var(--muted);
}

.checkbox-list {
  display: grid;
  gap: 0.35rem;
}

.checkbox-list label {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  color: var(--muted);
  font-weight: 500;
}

.checkbox-list input[type="checkbox"] {
  accent-color: var(--brand);
}

.tool-readout {
  margin-top: 0.2rem;
  border-top: 1px solid rgba(191, 208, 223, 0.75);
  padding-top: 0.65rem;
  display: grid;
  gap: 0.35rem;
  font-size: 0.92rem;
  color: var(--muted);
}

.tool-readout code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.plot-panel {
  background: rgba(255, 255, 255, 0.78);
  border: 1px solid rgba(191, 208, 223, 0.85);
  border-radius: 14px;
  padding: 0.35rem;
}

.plot-host {
  width: 100%;
  min-height: 620px;
}

.plot-caption {
  padding: 0.35rem 0.5rem 0.55rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.tiny-note {
  font-size: 0.85rem;
  color: var(--muted);
}
@media (max-width: 1000px) {
  .header-shell {
    grid-template-columns: 1fr;
  }

  .path-grid,
  .tutorial-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .technique-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .glossary-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .article-header-shell {
    grid-template-columns: 1fr;
  }

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

  .article-toc {
    position: static;
  }

  .subgrid-2,
  .diagram-grid,
  .notation-list {
    grid-template-columns: 1fr;
  }

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

@media (max-width: 640px) {
  .site-nav ul {
    gap: 0.2rem;
    padding: 0.5rem;
  }

  .site-nav a {
    padding: 0.5rem 0.65rem;
    font-size: 0.95rem;
  }

  .brand-block,
  .hero-panel {
    padding: 0.95rem;
  }

  .search-strip .section-shell,
  .section-alt .section-shell {
    padding: 0.9rem;
  }

  .path-grid,
  .fundamental-grid,
  .tutorial-grid,
  .technique-grid,
  .glossary-list {
    grid-template-columns: 1fr;
  }

  .btn {
    width: 100%;
  }

  .hero-actions {
    width: 100%;
  }

  .article-hero,
  .article-meta-panel,
  .article-panel,
  .article-toc {
    padding: 0.85rem;
  }

  .tool-controls {
    padding: 0.7rem;
  }

  .plot-host {
    min-height: 520px;
  }
}

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

  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }
}