/* ============================================================
   CSS CUSTOM PROPERTIES
   ============================================================ */
:root {
  /* Brand colors */
  --color-black:        #000000;
  --color-prussian:     #14213D;
  --color-orange:       #FCA311;
  --color-alabaster:    #E5E5E5;
  --color-white:        #FFFFFF;

  /* Extended palette */
  --color-bg:           #F8F9FA;
  --color-surface:      #FFFFFF;
  --color-border:       #E5E5E5;
  --color-text-primary: #000000;
  --color-text-muted:   #4A5568;
  --color-text-label:   #14213D;
  --color-accent:       #FCA311;
  --color-accent-pale:  #FEF3C7;

  /* Callout variants */
  --color-warning:      #F59E0B;
  --color-warning-pale: #FFFBEB;
  --color-tip:          #3B82F6;
  --color-tip-pale:     #EFF6FF;
  --color-fact-pale:    #F0F4FF;

  /* Python vs Java comparison */
  --color-python-bg:    #F0FFF4;
  --color-python-border:#86EFAC;
  --color-java-bg:      #EFF6FF;
  --color-java-border:  #93C5FD;

  /* Code block (Darcula-inspired) */
  --color-code-bg:      #2B2B2B;
  --color-code-text:    #A9B7C6;
  --color-code-kw:      #CC7832;
  --color-code-str:     #6A8759;
  --color-code-num:     #6897BB;
  --color-code-cmt:     #808080;

  /* Typography */
  --font-body:  'Inter', system-ui, sans-serif;
  --font-code:  'JetBrains Mono', 'Consolas', monospace;

  --text-xs:   0.75rem;
  --text-sm:   0.875rem;
  --text-base: 1rem;
  --text-lg:   1.125rem;
  --text-xl:   1.25rem;
  --text-2xl:  1.5rem;
  --text-3xl:  1.875rem;
  --text-4xl:  2.25rem;

  /* Spacing */
  --section-pad-y:        80px;
  --section-pad-y-mobile: 48px;

  /* Nav */
  --nav-height: 60px;
}

/* ============================================================
   BASE / RESET
   ============================================================ */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-text-primary);
  background-color: var(--color-bg);
  margin: 0;
  padding: 0;
  padding-top: var(--nav-height);
}

section {
  scroll-margin-top: calc(var(--nav-height) + 12px);
}

.topic-block,
.subtopic-block,
.concept-card,
.exercise-card {
  scroll-margin-top: calc(var(--nav-height) + 12px);
}

a {
  color: var(--color-prussian);
  text-decoration: none;
}

a:hover {
  color: var(--color-accent);
}

p {
  margin-bottom: 1rem;
  color: var(--color-text-primary);
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-body);
  font-weight: 700;
  color: var(--color-text-label);
  line-height: 1.3;
}

code, pre {
  font-family: var(--font-code);
}

img {
  max-width: 100%;
  height: auto;
}

ul, ol {
  padding-left: 1.5rem;
}

/* ============================================================
   SCROLL PROGRESS BAR
   ============================================================ */
#progress-bar {
  position: fixed;
  top: auto;
  left: 0;
  width: 0%;
  bottom: 0;
  height: 4px;
  background-color: var(--color-accent);
  z-index: 10000;
  transition: width 0.05s linear;
}

/* ============================================================
   NAVIGATION
   ============================================================ */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 9000;
  background-color: color-mix(in srgb, var(--color-prussian) 92%, transparent);
  height: var(--nav-height);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  box-shadow: 0 6px 24px rgba(0,0,0,0.08), 0 1px 0 rgba(255,255,255,0.08);
}

/* ============================================================
   FOOTER
   ============================================================ */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 40px 0 72px; /* extra bottom space for fixed buttons */
}

.site-footer-text {
  margin: 0;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.site-footer-link {
  color: var(--color-accent);
  font-weight: 700;
  text-decoration: none;
}

.site-footer-link:hover {
  color: var(--color-prussian);
  text-decoration: underline;
}

.site-brand {
  display: flex;
  align-items: baseline;
  gap: 6px;
  color: var(--color-white) !important;
  font-weight: 700;
  font-size: var(--text-lg);
  text-decoration: none;
}

.brand-name {
  color: var(--color-white);
}

.brand-by {
  font-size: var(--text-sm);
  font-weight: 400;
  color: rgba(255,255,255,0.5);
}

/* Hamburger toggler */
.navbar-toggler {
  border: 1px solid rgba(255,255,255,0.3);
  padding: 6px 10px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  background: transparent;
  cursor: pointer;
}

.navbar-toggler:focus {
  box-shadow: 0 0 0 2px rgba(252,163,17,0.5);
  outline: none;
}

.toggler-icon {
  display: block;
  width: 20px;
  height: 2px;
  background-color: rgba(255,255,255,0.8);
  border-radius: 1px;
}

/* Nav links */
#nav-links {
  gap: 4px;
}

.nav-link-item {
  list-style: none;
}

.nav-link-item a {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  font-size: var(--text-sm);
  font-weight: 500;
  color: rgba(255,255,255,0.75) !important;
  border-radius: 4px;
  text-decoration: none;
  transition: color 0.15s, background-color 0.15s;
  border-bottom: 2px solid transparent;
}

.nav-link-item a:hover {
  color: var(--color-white) !important;
  background-color: rgba(255,255,255,0.08);
}

.nav-link-item a.active {
  color: var(--color-accent) !important;
  border-bottom-color: var(--color-accent);
}

.nav-link-item a svg {
  width: 14px;
  height: 14px;
  flex-shrink: 0;
}

@media (max-width: 991px) {
  .navbar-collapse {
    background-color: var(--color-prussian);
    padding: 12px 0 16px;
    border-top: 1px solid rgba(255,255,255,0.1);
  }

  #nav-links {
    flex-direction: column;
    gap: 2px;
  }

  .nav-link-item a {
    border-bottom: none;
    border-left: 2px solid transparent;
    border-radius: 0 4px 4px 0;
    padding: 8px 16px;
  }

  .nav-link-item a.active {
    border-bottom: none;
    border-left-color: var(--color-accent);
    background-color: rgba(252,163,17,0.08);
  }
}

/* ============================================================
   HERO SECTION
   ============================================================ */
.hero-section {
  background-color: var(--color-surface);
  padding: 80px 0 60px;
  border-bottom: 1px solid var(--color-border);
}

@media (min-width: 992px) {
  .hero-section {
    min-height: 560px;
  }
}

.hero-left {
  padding-right: 40px;
}

.hero-eyebrow {
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: 12px;
}

.hero-title {
  font-size: var(--text-4xl);
  font-weight: 700;
  color: var(--color-prussian);
  line-height: 1.1;
  margin-bottom: 8px;
}

@media (min-width: 992px) {
  .hero-title {
    font-size: 3.5rem;
  }
}

.hero-tagline {
  font-size: var(--text-xl);
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: 16px;
}

.hero-description {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-bottom: 28px;
  max-width: 480px;
}

.hero-ctas {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn-hero-primary {
  background-color: var(--color-accent);
  color: var(--color-prussian);
  font-weight: 600;
  font-size: var(--text-sm);
  padding: 10px 24px;
  border-radius: 6px;
  border: 2px solid var(--color-accent);
  transition: background-color 0.15s, transform 0.1s;
  text-decoration: none;
}

.btn-hero-primary:hover {
  background-color: #e8950a;
  border-color: #e8950a;
  color: var(--color-prussian);
  transform: translateY(-1px);
}

.btn-hero-outline {
  background-color: transparent;
  color: var(--color-prussian);
  font-weight: 600;
  font-size: var(--text-sm);
  padding: 10px 24px;
  border-radius: 6px;
  border: 2px solid var(--color-prussian);
  transition: background-color 0.15s, color 0.15s, transform 0.1s;
  text-decoration: none;
}

.btn-hero-outline:hover {
  background-color: var(--color-prussian);
  color: var(--color-white);
  transform: translateY(-1px);
}

/* Hero code card */
.hero-right {
  justify-content: flex-end;
  align-items: center;
}

.hero-code-card {
  width: 100%;
  max-width: 440px;
  background-color: var(--color-code-bg);
  border-radius: 10px;
  overflow: hidden;
  border: 1px solid rgba(255,255,255,0.06);
}

.hero-code-card-header {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 10px 14px;
  background-color: rgba(255,255,255,0.05);
  border-bottom: 1px solid rgba(255,255,255,0.06);
}

.hero-code-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background-color: rgba(255,255,255,0.15);
}

.hero-code-label {
  font-family: var(--font-code);
  font-size: var(--text-xs);
  color: rgba(255,255,255,0.4);
  margin-left: 4px;
}

.hero-code-body {
  padding: 20px;
  min-height: 220px;
}

.hero-code-body pre {
  margin: 0;
  background: transparent !important;
  padding: 0 !important;
  font-size: 13px;
  line-height: 1.6;
  overflow: auto;
  max-height: 100%;
  white-space: pre;
  word-break: normal;
}

.hero-code-body code {
  background: transparent !important;
  font-size: 13px;
  white-space: pre;
}

@media (min-width: 992px) {
  .hero-code-card {
    max-width: 460px;
  }

  .hero-code-body {
    height: 260px;
    min-height: 260px;
    overflow: hidden;
  }

  .hero-code-body pre {
    height: 100%;
  }
}

/* ============================================================
   SECTION LAYOUT
   ============================================================ */
.content-section {
  padding: var(--section-pad-y) 0;
  border-bottom: 1px solid var(--color-border);
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.4s ease, transform 0.4s ease;
}

.content-section.section-visible {
  opacity: 1;
  transform: translateY(0);
}

.section-header {
  margin-bottom: 40px;
  padding-left: 20px;
  border-left: 4px solid var(--color-accent);
}

.section-number {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-text-muted);
  margin-bottom: 6px;
}

.section-title {
  font-size: var(--text-3xl);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 6px;
  line-height: 1.2;
}

.section-tagline {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  margin: 0;
  font-weight: 400;
}

.section-intro {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-bottom: 40px;
  max-width: 720px;
}

/* Topic blocks */
.topic-block {
  margin-bottom: 48px;
}

.topic-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 4px;
}

.topic-subtitle {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: 20px;
  font-style: italic;
}

/* ============================================================
   CODE BLOCKS
   ============================================================ */
.code-block-wrapper {
  margin: 20px 0;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid rgba(255,255,255,0.06);
}

.code-block-label {
  display: inline-block;
  font-family: var(--font-code);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  background-color: var(--color-alabaster);
  border: 1px solid var(--color-border);
  border-bottom: none;
  padding: 4px 12px;
  border-radius: 4px 4px 0 0;
  margin-bottom: 0;
}

.code-block-inner {
  position: relative;
  background-color: var(--color-code-bg);
  border-top: 4px solid var(--color-accent);
  border-radius: 0 8px 8px 8px;
}

.code-block-label + .code-block-inner {
  border-radius: 0 8px 8px 8px;
}

.code-block-inner pre {
  margin: 0;
  padding: 20px !important;
  background: transparent !important;
  overflow-x: auto;
  font-size: 13.5px;
  line-height: 1.6;
}

.code-block-inner code {
  font-family: var(--font-code);
  font-size: 13.5px;
  background: transparent !important;
}

/* Copy button */
.copy-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: 4px;
  padding: 4px 8px;
  cursor: pointer;
  color: rgba(255,255,255,0.5);
  transition: color 0.15s, background-color 0.15s;
  line-height: 1;
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: var(--text-xs);
}

.copy-btn:hover {
  background: rgba(255,255,255,0.14);
  color: rgba(255,255,255,0.8);
}

.copy-btn.copied {
  color: var(--color-accent);
}

.copy-btn svg {
  width: 14px;
  height: 14px;
}

/* Output block */
.code-output {
  background-color: #1e1e1e;
  border-top: 1px solid rgba(255,255,255,0.06);
  padding: 12px 20px;
}

.code-output-label {
  font-family: var(--font-code);
  font-size: var(--text-xs);
  color: rgba(255,255,255,0.3);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 6px;
}

.code-output-lines {
  font-family: var(--font-code);
  font-size: 13px;
  color: #98c379;
  line-height: 1.6;
  margin: 0;
  white-space: pre;
}

/* Side-by-side code layout */
.code-side-by-side {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}

@media (max-width: 767px) {
  .code-side-by-side {
    grid-template-columns: 1fr;
  }
}

/* ============================================================
   CALLOUT BLOCKS
   ============================================================ */
.callout {
  display: flex;
  gap: 14px;
  padding: 16px 18px;
  border-radius: 6px;
  margin: 20px 0;
  border-left-width: 4px;
  border-left-style: solid;
}

.callout-icon {
  flex-shrink: 0;
  margin-top: 2px;
}

.callout-icon svg {
  width: 18px;
  height: 18px;
}

.callout-text {
  font-size: var(--text-sm);
  line-height: 1.65;
  margin: 0;
}

.callout-key {
  background-color: var(--color-accent-pale);
  border-left-color: var(--color-accent);
}

.callout-key .callout-icon { color: var(--color-accent); }

.callout-warning {
  background-color: var(--color-warning-pale);
  border-left-color: var(--color-warning);
}

.callout-warning .callout-icon { color: var(--color-warning); }

.callout-tip {
  background-color: var(--color-tip-pale);
  border-left-color: var(--color-tip);
}

.callout-tip .callout-icon { color: var(--color-tip); }

.callout-fact {
  background-color: var(--color-fact-pale);
  border-left-color: var(--color-prussian);
}

.callout-fact .callout-icon { color: var(--color-prussian); }

/* ============================================================
   COMPARISON TABLES
   ============================================================ */
.comparison-table-wrapper {
  margin: 20px 0;
  overflow-x: auto;
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--color-border);
  font-size: var(--text-sm);
}

.comparison-table th {
  padding: 12px 16px;
  font-weight: 600;
  font-size: var(--text-sm);
  letter-spacing: 0.03em;
  text-align: left;
}

.comparison-table th.th-feature {
  background-color: var(--color-alabaster);
  color: var(--color-text-muted);
  width: 22%;
}

.comparison-table th.th-left {
  background-color: var(--color-python-bg);
  color: #166534;
  border-bottom: 2px solid var(--color-python-border);
}

.comparison-table th.th-right {
  background-color: var(--color-java-bg);
  color: #1e3a8a;
  border-bottom: 2px solid var(--color-java-border);
}

.comparison-table td {
  padding: 11px 16px;
  vertical-align: top;
  border-top: 1px solid var(--color-border);
  line-height: 1.6;
}

.comparison-table td.td-feature {
  font-weight: 600;
  color: var(--color-text-label);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  background-color: #fafafa;
}

.comparison-table tbody tr:nth-child(even) td:not(.td-feature) {
  background-color: rgba(229,229,229,0.25);
}

/* Mobile: stacked comparison cards */
@media (max-width: 575px) {
  .comparison-table,
  .comparison-table thead,
  .comparison-table tbody,
  .comparison-table tr,
  .comparison-table th,
  .comparison-table td {
    display: block;
    width: 100%;
  }

  .comparison-table thead {
    display: none;
  }

  .comparison-table tr {
    margin-bottom: 12px;
    border: 1px solid var(--color-border);
    border-radius: 8px;
    overflow: hidden;
  }

  .comparison-table td {
    border-top: 1px solid var(--color-border);
    padding: 10px 14px;
  }

  .comparison-table td.td-feature {
    background-color: var(--color-alabaster);
    border-top: none;
  }

  .comparison-table td:nth-child(2)::before {
    content: attr(data-left-label) ': ';
    font-weight: 600;
    color: #166534;
    display: block;
    font-size: var(--text-xs);
    text-transform: uppercase;
    margin-bottom: 4px;
  }

  .comparison-table td:nth-child(3)::before {
    content: attr(data-right-label) ': ';
    font-weight: 600;
    color: #1e3a8a;
    display: block;
    font-size: var(--text-xs);
    text-transform: uppercase;
    margin-bottom: 4px;
  }
}

/* ============================================================
   STEPS
   ============================================================ */
.steps-list {
  list-style: none;
  padding: 0;
  margin: 20px 0;
  position: relative;
}

.steps-list::before {
  content: '';
  position: absolute;
  left: 19px;
  top: 24px;
  bottom: 24px;
  width: 2px;
  background-color: var(--color-border);
}

.step-item {
  display: flex;
  gap: 16px;
  margin-bottom: 20px;
  position: relative;
}

.step-number {
  flex-shrink: 0;
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background-color: var(--color-prussian);
  color: var(--color-white);
  font-weight: 700;
  font-size: var(--text-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1;
}

.step-body {
  padding-top: 6px;
  flex: 1;
}

.step-label {
  font-weight: 600;
  color: var(--color-text-label);
  margin-bottom: 4px;
  font-size: var(--text-base);
}

.step-detail {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
  margin-bottom: 6px;
}

.step-artifact {
  display: inline-block;
  font-family: var(--font-code);
  font-size: var(--text-xs);
  background-color: var(--color-accent-pale);
  color: var(--color-prussian);
  border: 1px solid rgba(252,163,17,0.3);
  padding: 2px 8px;
  border-radius: 4px;
}

/* ============================================================
   LISTS
   ============================================================ */
.styled-list {
  list-style: none;
  padding: 0;
  margin: 16px 0;
}

.styled-list li {
  display: flex;
  gap: 10px;
  margin-bottom: 10px;
  font-size: var(--text-sm);
  line-height: 1.65;
}

.styled-list li::before {
  content: '';
  flex-shrink: 0;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background-color: var(--color-accent);
  margin-top: 7px;
}

/* Cards-style list */
.list-cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  list-style: none;
  padding: 0;
  margin: 16px 0;
}

@media (min-width: 768px) {
  .list-cards {
    grid-template-columns: 1fr 1fr;
  }
}

.list-card-item {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 16px;
  border-left: 3px solid var(--color-accent);
}

.list-card-label {
  font-weight: 600;
  color: var(--color-prussian);
  font-size: var(--text-sm);
  margin-bottom: 4px;
}

.list-card-detail {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
  margin: 0;
}

/* Relevance block: responsive 1 -> 2 -> 4 card grid */
#topic-relevance .list-cards {
  align-items: stretch;
}

#topic-relevance .list-card-item {
  height: 100%;
}

@media (min-width: 992px) {
  #topic-relevance .list-cards {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

/* Rules-style list */
.list-rules-group {
  margin: 16px 0;
}

.list-rules-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 10px;
}

.list-rules {
  list-style: none;
  padding: 0;
  margin: 0;
}

.list-rules li {
  display: flex;
  gap: 10px;
  padding: 10px 0;
  border-bottom: 1px solid var(--color-border);
  font-size: var(--text-sm);
}

.list-rules li:last-child {
  border-bottom: none;
}

.list-rules li::before {
  content: '';
  flex-shrink: 0;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background-color: var(--color-accent);
  margin-top: 7px;
}

.rule-label {
  font-weight: 600;
  color: var(--color-text-label);
  display: block;
  margin-bottom: 2px;
}

.rule-detail {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
}

/* ============================================================
   BREAKDOWN TABLE
   ============================================================ */
.breakdown-table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: var(--text-base);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  overflow: hidden;
}

.breakdown-table th {
  background-color: var(--color-prussian);
  color: var(--color-white);
  padding: 12px 18px;
  text-align: left;
  font-weight: 600;
  font-size: var(--text-sm);
  text-transform: uppercase;
  letter-spacing: 0.07em;
}

.breakdown-table td {
  padding: 14px 18px;
  border-top: 1px solid var(--color-border);
  vertical-align: top;
  line-height: 1.75;
}

.breakdown-table td:first-child {
  font-family: var(--font-code);
  font-size: 14.5px;
  background-color: var(--color-white);
  border-right: 1px solid var(--color-border);
  white-space: normal;
  word-break: break-word;
  width: 35%;
}

.breakdown-table td:first-child code {
  font-family: var(--font-code);
  font-size: 14.5px;
  line-height: 1.7;
  color: var(--color-black);
  font-weight: 600;
  background: transparent;
  padding: 0;
  text-shadow: none;
}

.breakdown-table td:first-child code .token.keyword {
  color: var(--color-code-kw);
}

.breakdown-table td:first-child code .token.class-name,
.breakdown-table td:first-child code .token.function {
  color: var(--color-black);
}

.breakdown-table td:first-child code .token.string {
  color: var(--color-code-str);
}

.breakdown-table td:first-child code .token.number {
  color: var(--color-code-num);
}

.breakdown-table td:first-child code .token.comment {
  color: var(--color-black);
}

.breakdown-table tbody tr:nth-child(even) td:last-child {
  background-color: rgba(229,229,229,0.2);
}

/* ============================================================
   GENERIC BOOTSTRAP TABLE OVERRIDES
   ============================================================ */
.content-table {
  font-size: var(--text-sm);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  overflow: hidden;
  margin: 20px 0;
}

.content-table th {
  background-color: var(--color-prussian);
  color: var(--color-white);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  border-color: rgba(255,255,255,0.1);
}

.content-table td {
  font-size: var(--text-sm);
  vertical-align: middle;
  border-color: var(--color-border);
}

.content-table td:first-child {
  font-family: var(--font-code);
  font-weight: 600;
  color: var(--color-prussian);
}

.content-table tbody tr:nth-child(even) {
  background-color: rgba(229,229,229,0.2);
}

.priority-high {
  font-weight: 600;
  color: var(--color-prussian);
}

/* ============================================================
   KEYWORD GRID
   ============================================================ */
.keyword-grid-block {
  margin: 18px 0 22px;
}

.keyword-grid-title {
  font-size: var(--text-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-bottom: 10px;
}

.keyword-grid {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 8px;
}

.keyword-chip {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 36px;
  padding: 8px 10px;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  background-color: var(--color-surface);
  font-family: var(--font-code);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-prussian);
}

@media (max-width: 991px) {
  .keyword-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (max-width: 767px) {
  .keyword-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 575px) {
  .keyword-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* ============================================================
   SUBTOPIC
   ============================================================ */
.subtopic-block {
  margin: 24px 0;
  padding-left: 20px;
  border-left: 2px solid var(--color-border);
}

.subtopic-title {
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--color-prussian);
  margin-bottom: 12px;
}

/* ============================================================
   TYPE DETAIL CARDS
   ============================================================ */
.type-detail-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 20px 24px;
  margin: 16px 0;
  border-top: 3px solid var(--color-accent);
}

.type-detail-header {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 12px;
}

.type-name {
  font-family: var(--font-code);
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-code-kw);
  background-color: var(--color-code-bg);
  padding: 2px 10px;
  border-radius: 4px;
}

.type-tagline {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
}

/* ============================================================
   DIAGRAM EMBEDS
   ============================================================ */
.diagram-figure {
  margin: 28px 0;
  text-align: center;
}

.diagram-wrapper {
  overflow-x: auto;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  background-color: var(--color-surface);
  padding: 16px;
  display: block;
  max-width: 100%;
  line-height: 0;
}

.diagram-wrapper svg {
  max-width: 100%;
  width: 100%;
  height: auto;
  border-radius: 4px;
  display: block;
}

.diagram-error {
  margin: 0;
  padding: 12px;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.5;
}

.diagram-figure figcaption {
  margin-top: 10px;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
}

/* ============================================================
   CONCEPT CARDS (conditionals + loops)
   ============================================================ */
.concept-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 28px 32px;
  margin-bottom: 32px;
}

.concept-header {
  margin-bottom: 20px;
}

.concept-keyword {
  font-family: var(--font-code);
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-accent);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  display: block;
  margin-bottom: 6px;
}

.concept-syntax {
  font-family: var(--font-code);
  font-size: var(--text-base);
  color: var(--color-prussian);
  font-weight: 600;
  background-color: var(--color-accent-pale);
  border: 1px solid rgba(252,163,17,0.3);
  padding: 6px 14px;
  border-radius: 4px;
  display: inline-block;
}

.concept-explanation {
  font-size: var(--text-base);
  color: var(--color-text-primary);
  line-height: 1.7;
  margin: 16px 0;
}

.concept-section-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin: 20px 0 10px;
}

.concept-use-cases,
.concept-key-points {
  list-style: none;
  padding: 0;
  margin: 0;
}

.concept-use-cases li,
.concept-key-points li {
  display: flex;
  gap: 10px;
  margin-bottom: 8px;
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-text-primary);
}

.concept-use-cases li::before,
.concept-key-points li::before {
  content: '';
  flex-shrink: 0;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background-color: var(--color-accent);
  margin-top: 7px;
}

.concept-example {
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid var(--color-border);
}

.concept-example-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: 4px;
}

.concept-example-scenario {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
  margin-bottom: 12px;
}

/* Common causes (infinite loops) */
.common-cause-item {
  margin: 16px 0;
  background-color: #fafafa;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  overflow: hidden;
}

.common-cause-label {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-prussian);
  padding: 10px 16px;
  background-color: var(--color-alabaster);
  border-bottom: 1px solid var(--color-border);
}

.common-cause-fix {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  padding: 10px 16px;
  border-top: 1px solid var(--color-border);
  background-color: var(--color-tip-pale);
}

.common-cause-fix::before {
  content: 'Fix: ';
  font-weight: 600;
  color: var(--color-tip);
}

/* ============================================================
   EXERCISE CARDS
   ============================================================ */
.exercises-section {
  margin-top: 40px;
  padding-top: 32px;
  border-top: 1px solid var(--color-border);
}

.exercises-heading {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 20px;
}

.exercise-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 24px;
  margin-bottom: 16px;
}

.exercise-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.exercise-title {
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-prussian);
  margin: 0;
}

.level-badge {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 3px 10px;
  border-radius: 20px;
  flex-shrink: 0;
}

.level-starter {
  background-color: #DCFCE7;
  color: #166534;
  border: 1px solid #86EFAC;
}

.level-build {
  background-color: #FEF3C7;
  color: #92400E;
  border: 1px solid #FCD34D;
}

.level-challenge {
  background-color: #FEE2E2;
  color: #991B1B;
  border: 1px solid #FCA5A5;
}

.exercise-scenario {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.65;
  margin-bottom: 12px;
}

.exercise-requirements {
  list-style: none;
  padding: 0;
  margin: 0 0 16px;
}

.exercise-requirements li {
  display: flex;
  gap: 8px;
  font-size: var(--text-sm);
  color: var(--color-text-primary);
  line-height: 1.6;
  margin-bottom: 6px;
}

.exercise-requirements li::before {
  content: '→';
  color: var(--color-accent);
  font-weight: 700;
  flex-shrink: 0;
}

.reveal-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-accent);
  background-color: transparent;
  border: 2px solid var(--color-accent);
  border-radius: 6px;
  padding: 8px 18px;
  cursor: pointer;
  transition: background-color 0.15s, color 0.15s;
  margin-top: 4px;
}

.reveal-btn:hover {
  background-color: var(--color-accent);
  color: var(--color-prussian);
}

.reveal-btn svg {
  width: 15px;
  height: 15px;
}

.solution-panel {
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid var(--color-border);
  overflow: hidden;
}

.solution-explanation {
  background-color: var(--color-accent-pale);
  border-left: 4px solid var(--color-accent);
  padding: 14px 18px;
  border-radius: 0 6px 6px 0;
  margin-top: 16px;
}

.solution-explanation p {
  font-size: var(--text-sm);
  color: var(--color-text-primary);
  line-height: 1.65;
  margin: 0;
}

/* ============================================================
   QUICK REFERENCE SECTION
   ============================================================ */
.quick-ref-groups {
  display: flex;
  flex-direction: column;
  gap: 40px;
}

.quick-ref-group-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--color-border);
}

.quick-ref-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}

@media (min-width: 576px) {
  .quick-ref-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (min-width: 992px) {
  .quick-ref-grid {
    grid-template-columns: 1fr 1fr 1fr;
  }
}

.quick-ref-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: 16px 18px;
}

.quick-ref-title {
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  margin-bottom: 8px;
}

.quick-ref-syntax {
  font-family: var(--font-code);
  font-size: 12.5px;
  color: var(--color-code-text);
  background-color: var(--color-code-bg);
  padding: 8px 12px;
  border-radius: 4px;
  margin-bottom: 8px;
  overflow-x: auto;
  white-space: pre;
  display: block;
  line-height: 1.6;
}

.quick-ref-desc {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  line-height: 1.55;
  margin: 0;
}

/* ============================================================
   REFERENCES SECTION
   ============================================================ */
.references-groups {
  display: flex;
  flex-direction: column;
  gap: 40px;
}

.ref-group-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--color-border);
}

.ref-list {
  list-style: none;
  padding: 0;
  margin: 0 0 24px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.ref-item {
  display: flex;
  gap: 14px;
  padding: 14px 16px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  align-items: flex-start;
}

.ref-type-badge {
  flex-shrink: 0;
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  padding: 3px 8px;
  border-radius: 3px;
  margin-top: 2px;
}

.ref-type-official {
  background-color: #EFF6FF;
  color: #1e3a8a;
  border: 1px solid #93C5FD;
}

.ref-type-tutorial {
  background-color: #F0FFF4;
  color: #166534;
  border: 1px solid #86EFAC;
}

.ref-type-article {
  background-color: #FEF3C7;
  color: #92400E;
  border: 1px solid #FCD34D;
}

.ref-type-community {
  background-color: var(--color-fact-pale);
  color: var(--color-prussian);
  border: 1px solid #C7D2FE;
}

.ref-type-reference {
  background-color: #F5F3FF;
  color: #4C1D95;
  border: 1px solid #C4B5FD;
}

.ref-content {
  flex: 1;
  min-width: 0;
}

.ref-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-prussian);
  margin-bottom: 2px;
}

.ref-title a {
  color: var(--color-prussian);
  text-decoration: none;
}

.ref-title a:hover {
  color: var(--color-accent);
  text-decoration: underline;
}

.ref-author {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-bottom: 4px;
}

.ref-description {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  line-height: 1.55;
  margin: 0;
}

.further-reading-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin-bottom: 10px;
}

.further-reading-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.further-reading-item a {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-prussian);
}

.further-reading-item a:hover {
  color: var(--color-accent);
}

.further-reading-item p {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin: 2px 0 0;
}

/* General resources grid */
.general-resources {
  margin-top: 40px;
  padding-top: 32px;
  border-top: 1px solid var(--color-border);
}

.general-resources-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 20px;
}

/* ============================================================
   FLOATING BUTTONS
   ============================================================ */
.float-btn {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--color-prussian);
  transition: background-color 0.15s, box-shadow 0.15s, transform 0.15s;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.float-btn:hover {
  background-color: var(--color-prussian);
  color: var(--color-white);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.float-btn svg {
  width: 16px;
  height: 16px;
}

#back-to-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 9999;
}

/* Gear button + toggle wrapper */
#section-toggle-wrapper {
  position: fixed;
  bottom: 20px;
  left: 20px;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 8px;
}

#gear-btn {
  transition: transform 0.25s ease, background-color 0.15s, color 0.15s;
}

#gear-btn.open {
  transform: rotate(90deg);
}

/* Section toggle panel */
#section-toggle-panel {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  padding: 16px;
  width: 220px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.12);
  margin-bottom: 4px;
}

/* ============================================================
   Docs TOC (Table of Contents)
   ============================================================ */
#toc-toggle-wrapper {
  position: fixed;
  top: calc(var(--nav-height) + 16px);
  right: 20px;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 8px;
}

#toc-toggle-panel {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  width: 300px;
  max-height: calc(100vh - var(--nav-height) - 32px);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: 0 4px 20px rgba(0,0,0,0.12);
  margin-bottom: 4px;
}

/* Tab header */
.toc-panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--color-border);
  padding: 0 12px;
  flex-shrink: 0;
}

/* Search bar */
.toc-search-wrapper {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
}

.toc-search-icon {
  flex-shrink: 0;
  width: 14px;
  height: 14px;
  color: var(--color-text-muted);
}

.toc-search-input {
  flex: 1;
  border: none;
  outline: none;
  background: transparent;
  font-family: var(--font-body);
  font-size: var(--text-sm);
  color: var(--color-text-primary);
  line-height: 1.5;
  appearance: none;
  -webkit-appearance: none;
}

.toc-search-input::placeholder {
  color: var(--color-text-muted);
}

.toc-search-input::-webkit-search-cancel-button {
  cursor: pointer;
}

/* Search results panel */
.toc-search-results {
  display: flex;
  flex-direction: column;
}

.toc-search-empty {
  padding: 24px 0;
  text-align: center;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

.toc-result-item {
  display: flex;
  flex-direction: column;
  gap: 1px;
  padding: 8px 10px;
  border-radius: 6px;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.1s;
}

.toc-result-item:hover {
  background-color: var(--color-alabaster);
}

.toc-result-row {
  display: flex;
  align-items: baseline;
  gap: 7px;
}

.toc-result-badge {
  flex-shrink: 0;
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 1px 6px;
  border-radius: 3px;
  line-height: 1.5;
}

.toc-badge-section  { background-color: var(--color-accent-pale); color: #92400E; }
.toc-badge-topic    { background-color: #EFF6FF; color: #1e3a8a; }
.toc-badge-concept  { background-color: #F0FFF4; color: #166534; }
.toc-badge-starter  { background-color: #F5F3FF; color: #4C1D95; }
.toc-badge-build    { background-color: var(--color-fact-pale); color: var(--color-prussian); }
.toc-badge-challenge{ background-color: #FFF0F0; color: #991B1B; }

.toc-result-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-prussian);
  line-height: 1.4;
}

.toc-result-title mark {
  background-color: var(--color-accent-pale);
  color: inherit;
  border-radius: 2px;
  padding: 0 1px;
}

.toc-result-context {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  padding-left: 2px;
}

.toc-tab-strip {
  display: flex;
  gap: 0;
}

.toc-tab {
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  padding: 10px 12px;
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
  margin-bottom: -1px;
  line-height: 1;
}

.toc-tab:hover {
  color: var(--color-prussian);
}

.toc-tab.active {
  color: var(--color-prussian);
  border-bottom-color: var(--color-accent);
}

.toc-close-btn {
  background: none;
  border: none;
  padding: 6px;
  cursor: pointer;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  border-radius: 4px;
  transition: color 0.15s, background-color 0.15s;
}

.toc-close-btn:hover {
  color: var(--color-prussian);
  background-color: var(--color-alabaster);
}

.toc-close-btn svg {
  width: 14px;
  height: 14px;
}

/* Tab panels */
.toc-tab-panel {
  flex: 1;
  overflow-y: auto;
  padding: 14px 14px 16px;
}

.docs-toc-content {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* Exercises tab — section group */
.toc-ex-section {
  padding-bottom: 4px;
}

.toc-ex-section-title {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-prussian);
  margin-bottom: 8px;
}

.toc-ex-level-group {
  margin-bottom: 10px;
}

.toc-ex-level-group summary {
  cursor: pointer;
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--color-text-muted);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 3px 0;
  user-select: none;
}

.toc-ex-level-group summary::-webkit-details-marker {
  display: none;
}

.toc-ex-level-group summary::before {
  content: '';
  display: inline-block;
  width: 6px;
  height: 6px;
  border-right: 1.5px solid currentColor;
  border-bottom: 1.5px solid currentColor;
  transform: rotate(-45deg);
  transition: transform 0.15s;
  flex-shrink: 0;
}

.toc-ex-level-group[open] summary::before {
  transform: rotate(45deg);
}

.toc-ex-level-list {
  list-style: none;
  padding: 0;
  margin: 4px 0 0 16px;
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.toc-ex-link {
  display: block;
  font-size: var(--text-sm);
  font-weight: 400;
  color: var(--color-text-muted);
  text-decoration: none;
  line-height: 1.5;
  padding: 1px 0;
}

.toc-ex-link:hover {
  color: var(--color-prussian);
  text-decoration: underline;
}

.docs-toc-section {
  padding-top: 8px;
}

.docs-toc-section-title {
  display: block;
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-prussian);
  text-decoration: none;
  margin-bottom: 6px;
}

.docs-toc-section-title:hover {
  color: var(--color-accent);
  text-decoration: underline;
}

.docs-toc-topic-list,
.docs-toc-subtopic-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.docs-toc-topic-item {
  margin-bottom: 4px;
}

.docs-toc-topic-link {
  display: block;
  font-size: var(--text-sm);
  line-height: 1.45;
  font-weight: 500;
  color: var(--color-text-muted);
  text-decoration: none;
  padding: 1px 0 1px 10px;
}

.docs-toc-topic-link:hover {
  color: var(--color-prussian);
  text-decoration: underline;
}

.docs-toc-subtopic-item {
  margin: 1px 0;
}

.docs-toc-subtopic-link {
  display: block;
  font-weight: 400;
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: var(--text-xs);
  line-height: 1.45;
  padding: 1px 0 1px 20px;
}

.docs-toc-subtopic-link:hover {
  color: var(--color-prussian);
  text-decoration: underline;
}

.docs-toc-problems-title {
  font-size: var(--text-xs);
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  margin-top: 4px;
  margin-bottom: 6px;
}

.toc-level-group {
  margin-bottom: 8px;
}

.toc-level-group summary {
  cursor: pointer;
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  list-style: none;
  line-height: 1.35;
}

.toc-level-group summary::-webkit-details-marker {
  display: none;
}

.toc-level-list {
  list-style: none;
  padding: 0;
  margin: 6px 0 0;
}

.toc-level-list li {
  margin: 3px 0;
}

.toc-problem-link {
  display: block;
  font-weight: 400;
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: var(--text-xs);
  line-height: 1.45;
  padding-left: 10px;
}

#toc-toggle-panel .toggle-panel-title {
  font-size: var(--text-base);
  font-weight: 700;
  letter-spacing: 0.01em;
}

.toc-problem-link:hover {
  color: var(--color-prussian);
  text-decoration: underline;
}

.toggle-panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
}

.toggle-panel-title {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-prussian);
}

.toggle-panel-actions {
  display: flex;
  gap: 6px;
}

.toggle-action-btn {
  font-size: 11px;
  font-weight: 600;
  color: var(--color-text-muted);
  background: none;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 2px 8px;
  cursor: pointer;
  transition: color 0.1s, border-color 0.1s;
}

.toggle-action-btn:hover {
  color: var(--color-prussian);
  border-color: var(--color-prussian);
}

.toggle-panel-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.toggle-panel-item label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: var(--text-sm);
  color: var(--color-text-primary);
  cursor: pointer;
  padding: 4px 0;
}

.toggle-panel-item input[type="checkbox"] {
  accent-color: var(--color-prussian);
  width: 14px;
  height: 14px;
  cursor: pointer;
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 991px) {
  .hero-section {
    padding: 32px 0 36px;
  }

  .hero-left {
    padding-right: 0;
  }

  .content-section {
    padding: var(--section-pad-y-mobile) 0;
  }

  .section-title {
    font-size: var(--text-2xl);
  }

  .concept-card {
    padding: 20px;
  }
}

/* ---- Tablet (576–767px) ---- */
@media (max-width: 767px) {
  /* TOC button: move to bottom-right stack (above back-to-top) */
  #toc-toggle-wrapper {
    top: auto;
    bottom: 72px;
    right: 20px;
    flex-direction: column-reverse;
  }

  /* Panel: near full-width, opens upward */
  #toc-toggle-panel {
    width: min(300px, calc(100vw - 32px));
    max-height: calc(100vh - var(--nav-height) - 140px);
    margin-bottom: 0;
    margin-top: 8px;
  }

  /* Back-to-top stays at 20px bottom-right, no change needed */

  /* Reduce section spacing */
  .section-header {
    margin-bottom: 28px;
  }

  /* Code side-by-side: force single column */
  .code-side-by-side {
    flex-direction: column !important;
  }

  /* Code block: tighter padding */
  .code-block-inner pre {
    padding: 14px 14px !important;
    font-size: 12.5px;
  }
}

/* ---- Mobile (< 576px) ---- */
@media (max-width: 575px) {
  .hero-title {
    font-size: var(--text-3xl);
  }

  .hero-tagline {
    font-size: var(--text-base);
  }

  .hero-description {
    font-size: var(--text-sm);
    margin-bottom: 20px;
  }

  .hero-section {
    padding: 24px 0 28px;
  }

  /* Hero stats row: stack on tiny screens */
  .hero-stats {
    flex-direction: row;
    flex-wrap: wrap;
    gap: 8px;
  }

  .hero-stat-badge {
    flex: 1 1 auto;
    justify-content: center;
    min-width: 90px;
  }

  .section-header {
    padding-left: 14px;
    margin-bottom: 24px;
  }

  .section-header-eyebrow {
    font-size: 10px;
  }

  .section-title {
    font-size: var(--text-xl);
  }

  .section-tagline {
    font-size: var(--text-sm);
  }

  .concept-card {
    padding: 16px;
  }

  .exercise-card {
    padding: 16px 14px;
  }

  .level-badge {
    font-size: 10px;
    padding: 3px 8px;
  }

  /* Code blocks: tighter */
  .code-block-wrapper {
    margin-bottom: 16px;
  }

  .code-block-label {
    font-size: 10px;
    padding: 4px 10px;
  }

  .code-block-inner pre {
    padding: 12px 12px !important;
    font-size: 12px;
  }

  /* Comparison table: already stacked, tighten up */
  .comparison-card {
    padding: 12px;
  }

  /* Quick ref grid: always 1 col on tiny */
  .quick-ref-grid {
    grid-template-columns: 1fr !important;
  }

  #section-toggle-panel {
    width: 190px;
  }

  /* TOC panel: use all available width */
  #toc-toggle-panel {
    width: calc(100vw - 24px);
    right: 12px;
  }

  #toc-toggle-wrapper {
    right: 12px;
  }
}

/* ============================================================
   PRINT STYLESHEET
   ============================================================ */
@media print {
  #progress-bar,
  .site-nav,
  #back-to-top,
  #section-toggle-wrapper,
  #toc-toggle-wrapper,
  .reveal-btn,
  .copy-btn {
    display: none !important;
  }

  .content-section {
    opacity: 1 !important;
    transform: none !important;
    page-break-inside: avoid;
  }

  body {
    background-color: #fff;
    color: #000;
  }

  .code-block-inner {
    border: 1px solid #ccc;
  }
}

/* ============================================================
   REDUCED MOTION
   ============================================================ */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .content-section {
    opacity: 1 !important;
    transform: none !important;
    transition: none !important;
  }

  * {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}