:root {
  --md-text-font: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --md-code-font: "JetBrains Mono", "SFMono-Regular", Consolas, monospace;
  --md-primary-fg-color: #ffffff;
  --md-primary-bg-color: #111827;
  --md-accent-fg-color: #4f46e5;
}

[data-md-color-scheme="slate"] {
  --md-primary-fg-color: #111827;
  --md-primary-bg-color: #f9fafb;
  --md-accent-fg-color: #818cf8;
}

.md-header {
  border-bottom: 1px solid var(--md-default-fg-color--lightest);
  box-shadow: none;
}

.md-sidebar--primary .md-nav__title {
  color: var(--md-default-fg-color--light);
  font-size: 0.64rem;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.md-sidebar--primary .md-nav__link {
  margin-top: 0.3rem;
  padding: 0.28rem 0.55rem;
  border-radius: 0.3rem;
  line-height: 1.45;
  transition: background-color 120ms ease, color 120ms ease;
}

.md-sidebar--primary .md-nav__link:hover {
  background: color-mix(in srgb, var(--md-accent-fg-color) 8%, transparent);
}

.md-sidebar--primary .md-nav__link--active {
  background: color-mix(in srgb, var(--md-accent-fg-color) 12%, transparent);
  font-weight: 700;
}

.md-sidebar--primary .book-section-start {
  --section-color: var(--md-accent-fg-color);
  margin-top: 0.75rem;
  padding-top: 0.72rem;
  border-top: 1px solid var(--md-default-fg-color--lightest);
}

.md-sidebar--primary .book-section-start > .md-nav__link {
  padding: 0.42rem 0.6rem;
  border-left: 3px solid var(--section-color);
  background: color-mix(in srgb, var(--section-color) 9%, transparent);
  color: var(--md-default-fg-color);
  font-weight: 750;
}

.md-sidebar--primary .book-section-1 { --section-color: #2563eb; }
.md-sidebar--primary .book-section-2 { --section-color: #7c3aed; }
.md-sidebar--primary .book-section-3 { --section-color: #db2777; }
.md-sidebar--primary .book-section-4 { --section-color: #059669; }
.md-sidebar--primary .book-section-5 { --section-color: #d97706; }
.md-sidebar--primary .book-section-appendix { --section-color: #64748b; }

.md-main__inner {
  max-width: 1440px;
}

.md-content__inner {
  max-width: 880px;
  margin-inline: auto;
  padding-bottom: 5rem;
}

.md-typeset {
  font-size: 0.78rem;
  line-height: 1.85;
}

.md-typeset h1 {
  margin-bottom: 1.6rem;
  font-weight: 750;
  letter-spacing: -0.025em;
}

.md-typeset h2 {
  margin-top: 2.4rem;
  padding-bottom: 0.35rem;
  border-bottom: 1px solid var(--md-default-fg-color--lightest);
  font-weight: 700;
}

.md-typeset h3 {
  font-weight: 650;
}

.md-typeset blockquote {
  border-left: 3px solid var(--md-accent-fg-color);
  color: var(--md-default-fg-color--light);
}

.md-typeset code {
  border-radius: 0.25rem;
}

.hero-copy {
  max-width: 760px;
  margin: -0.5rem 0 2.2rem;
  color: var(--md-default-fg-color--light);
  font-size: 1rem;
  line-height: 1.8;
}

.book-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  margin: 2rem 0 3rem;
}

.book-card {
  display: block;
  min-height: 210px;
  padding: 1.4rem;
  border: 1px solid var(--md-default-fg-color--lightest);
  border-radius: 0.75rem;
  color: inherit !important;
  text-decoration: none;
  transition: border-color 120ms ease, transform 120ms ease;
}

.book-card:hover {
  border-color: var(--md-accent-fg-color);
  transform: translateY(-2px);
}

.book-card h2 {
  margin: 0.8rem 0;
  padding: 0;
  border: 0;
  font-size: 1.1rem;
}

.book-card p {
  margin: 0;
  color: var(--md-default-fg-color--light);
  font-size: 0.72rem;
}

.book-number {
  color: var(--md-accent-fg-color);
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.08em;
}

@media screen and (max-width: 900px) {
  .book-grid {
    grid-template-columns: 1fr;
  }

  .book-card {
    min-height: auto;
  }
}

/* —— formula-flow nav / toc mark —— */
.formula-flow-mark {
  display: inline-block;
  width: 0.34rem;
  height: 0.34rem;
  margin-left: 0.38rem;
  border-radius: 0.05rem;
  background: var(--md-accent-fg-color);
  transform: rotate(45deg) translateY(-0.04rem);
  vertical-align: middle;
  opacity: 0.8;
  flex-shrink: 0;
}

.md-sidebar--secondary .md-nav__link.has-formula-flow,
.md-sidebar--primary .md-nav__link.has-formula-flow {
  align-items: center;
}

.md-sidebar--secondary .formula-flow-mark {
  width: 0.3rem;
  height: 0.3rem;
  margin-left: 0.3rem;
  opacity: 0.9;
}

/* —— formula data-flow panel —— */
.formula-flow-host {
  position: relative;
  margin: 1.15rem 0 1.5rem;
}

.formula-flow-host > .arithmatex {
  margin: 0;
  padding: 0.65rem 0.85rem 0.75rem;
  border: 1px solid transparent;
  border-radius: 0.6rem;
  transition: border-color 140ms ease, background-color 140ms ease, box-shadow 140ms ease;
}

.formula-flow-host:hover > .arithmatex,
.formula-flow-host.is-open > .arithmatex {
  border-color: color-mix(in srgb, var(--md-accent-fg-color) 42%, transparent);
  background: color-mix(in srgb, var(--md-accent-fg-color) 5%, transparent);
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--md-accent-fg-color) 8%, transparent);
}

.formula-flow-badge {
  position: absolute;
  top: 0.2rem;
  right: 0.2rem;
  z-index: 2;
  margin: 0;
  padding: 0.14rem 0.5rem;
  border: 1px solid color-mix(in srgb, var(--md-accent-fg-color) 38%, transparent);
  border-radius: 999px;
  background: var(--md-default-bg-color);
  color: var(--md-accent-fg-color);
  font: 650 0.58rem/1.4 var(--md-text-font);
  letter-spacing: 0.05em;
  cursor: pointer;
  opacity: 0.7;
  transition: opacity 120ms ease, background-color 120ms ease, transform 120ms ease;
}

.formula-flow-host:hover .formula-flow-badge,
.formula-flow-host.is-open .formula-flow-badge {
  opacity: 1;
  background: color-mix(in srgb, var(--md-accent-fg-color) 10%, var(--md-default-bg-color));
}

.formula-flow-host.is-open .formula-flow-badge {
  transform: translateY(-1px);
}

.formula-flow-pop {
  display: none;
  margin-top: 0.65rem;
  padding: 0.9rem 1rem 0.75rem;
  border: 1px solid var(--md-default-fg-color--lightest);
  border-radius: 0.75rem;
  background:
    linear-gradient(
      135deg,
      color-mix(in srgb, var(--md-accent-fg-color) 6%, transparent),
      transparent 42%
    ),
    var(--md-default-bg-color);
}

.formula-flow-host.is-open .formula-flow-pop {
  display: block;
  animation: formula-flow-in 200ms ease;
}

@keyframes formula-flow-in {
  from {
    opacity: 0;
    transform: translateY(-4px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.formula-flow-pop__head {
  margin-bottom: 0.7rem;
  padding-bottom: 0.55rem;
  border-bottom: 1px solid var(--md-default-fg-color--lightest);
}

.formula-flow-pop__title {
  font-weight: 750;
  font-size: 0.8rem;
  letter-spacing: -0.015em;
}

.formula-flow-pop__sub {
  margin-top: 0.22rem;
  color: var(--md-default-fg-color--light);
  font-size: 0.62rem;
}

.formula-flow-pop__rail {
  display: grid;
  gap: 0;
  margin: 0;
  padding: 0;
  list-style: none;
}

.formula-flow-pop__step {
  position: relative;
  margin: 0;
  padding: 0.5rem 0 0.5rem 0.95rem;
  border-left: 2px solid color-mix(in srgb, var(--md-accent-fg-color) 26%, transparent);
  opacity: 0;
  transform: translateY(6px);
}

.formula-flow-pop__step.is-in {
  opacity: 1;
  transform: translateY(0);
  transition: opacity 320ms ease, transform 320ms ease;
  transition-delay: calc(var(--step-i, 0) * 85ms);
}

.formula-flow-pop__step::before {
  content: "";
  position: absolute;
  left: -5px;
  top: 0.78rem;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--md-accent-fg-color);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--md-accent-fg-color) 16%, transparent);
}

.formula-flow-pop__step-top {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.3rem 0.55rem;
}

.formula-flow-pop__label {
  font-weight: 700;
  font-size: 0.7rem;
}

.formula-flow-pop__tex {
  padding: 0.06rem 0.3rem;
  border-radius: 0.28rem;
  background: color-mix(in srgb, var(--md-accent-fg-color) 10%, transparent);
  color: var(--md-default-fg-color);
  font-size: 0.62rem;
}

.formula-flow-pop__shape {
  margin-left: auto;
  color: var(--md-accent-fg-color);
  font-family: var(--md-code-font);
  font-size: 0.6rem;
  font-weight: 650;
}

.formula-flow-pop--wide {
  max-width: min(40rem, 100%);
}

.formula-flow-matrices {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem 0.75rem;
  margin-top: 0.35rem;
  align-items: flex-start;
}

.formula-flow-matrix {
  display: inline-flex;
  flex-direction: column;
  gap: 0.2rem;
  margin-top: 0.28rem;
}

.formula-flow-matrices .formula-flow-matrix {
  margin-top: 0;
}

.formula-flow-matrix__name {
  font-family: var(--md-code-font);
  font-size: 0.58rem;
  font-weight: 650;
  color: var(--md-accent-fg-color);
  letter-spacing: 0.02em;
}

.formula-flow-matrix__body {
  display: inline-grid;
  gap: 0.14rem 0.18rem;
  padding: 0.35rem 0.45rem;
  border: 1px solid color-mix(in srgb, var(--md-accent-fg-color) 28%, transparent);
  border-radius: 0.35rem;
  background: color-mix(in srgb, var(--md-default-fg-color) 3.5%, transparent);
  box-shadow:
    inset 3px 0 0 color-mix(in srgb, var(--md-accent-fg-color) 35%, transparent),
    inset -3px 0 0 color-mix(in srgb, var(--md-accent-fg-color) 35%, transparent);
}

.formula-flow-matrix__row {
  display: grid;
  grid-template-columns: repeat(var(--ff-cols, 2), minmax(2.2rem, auto));
  gap: 0.14rem 0.18rem;
}

.formula-flow-matrix__cell {
  min-width: 2.2rem;
  padding: 0.12rem 0.28rem;
  border-radius: 0.22rem;
  background: color-mix(in srgb, var(--md-default-bg-color) 70%, transparent);
  font-family: var(--md-code-font);
  font-size: 0.6rem;
  font-variant-numeric: tabular-nums;
  text-align: center;
  letter-spacing: -0.01em;
}

.formula-flow-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.28rem;
  margin-top: 0.28rem;
}

.formula-flow-chip {
  display: inline-block;
  min-width: 2.6rem;
  padding: 0.16rem 0.4rem;
  border-radius: 0.35rem;
  background: color-mix(in srgb, var(--md-default-fg-color) 5%, transparent);
  font-family: var(--md-code-font);
  font-size: 0.62rem;
  font-variant-numeric: tabular-nums;
  text-align: center;
  letter-spacing: -0.01em;
}

.formula-flow-pop__note {
  margin-top: 0.2rem;
  color: var(--md-default-fg-color--light);
  font-size: 0.58rem;
  line-height: 1.45;
}

.formula-flow-pop__foot {
  margin-top: 0.5rem;
  padding-top: 0.4rem;
  border-top: 1px solid var(--md-default-fg-color--lightest);
  color: var(--md-default-fg-color--light);
  font-size: 0.55rem;
}