:root {
  --bg-1: #eef8fc;
  --bg-2: #f5fbff;
  --bg-glow-1: #bae6fd;
  --bg-glow-2: #e0f2fe;
  --card-bg: #ffffff;
  --text: #1e2233;
  --muted: #6b7280;
  --accent: #0284c7;
  --accent-2: #38bdf8;
  --accent-3: #7dd3fc;
  --accent-soft: #e0f2fe;
  --accent-deep: #0369a1;
  --accent-border: #bae6fd;
  --accent-rgb: 2, 132, 199;
  --border: #e2eef5;
  --green: #16a34a;
  --green-soft: #ecfdf3;
  --lead: #3a3f52;
  --method-bg: #f0f9ff;
  --remark-bg: #f0fdfa;
  --remark-border: #99f6e4;
  --result-border: #86efac;
  --warn: #b45309;
  --warn-bar: #f59e0b;
  --surface-2: #fafbff;
  --domain-bg: #e0f2fe;
  --crumb-sep: #c5d0da;
  --radius: 20px;
  --shadow-sm: 0 1px 2px rgba(30, 34, 51, 0.04);
  --shadow-lg: 0 20px 45px -15px rgba(var(--accent-rgb), 0.16),
    0 8px 20px -8px rgba(30, 34, 51, 0.08);
  --max: 960px;
}

/* Topic palettes — same cool tone family, distinct hues */
[data-topic="first-order-differential-equations"],
[data-topic="differential-equations"] {
  --accent: #0e7490;
  --accent-2: #22d3ee;
  --accent-3: #67e8f9;
  --accent-soft: #cffafe;
  --accent-deep: #155e75;
  --accent-border: #a5f3fc;
  --accent-rgb: 14, 116, 144;
  --bg-1: #ecfeff;
  --bg-2: #f0fdfa;
  --bg-glow-1: #a5f3fc;
  --bg-glow-2: #ccfbf1;
  --border: #d5f5f6;
}

[data-topic="second-order-differential-equations"] {
  --accent: #155e75;
  --accent-2: #22d3ee;
  --accent-3: #67e8f9;
  --accent-soft: #cffafe;
  --accent-deep: #164e63;
  --accent-border: #a5f3fc;
  --accent-rgb: 21, 94, 117;
  --bg-1: #ecfeff;
  --bg-2: #f0f9ff;
  --bg-glow-1: #a5f3fc;
  --bg-glow-2: #bae6fd;
  --border: #d5f5f6;
}

[data-topic="systems-of-differential-equations"] {
  --accent: #0f766e;
  --accent-2: #14b8a6;
  --accent-3: #5eead4;
  --accent-soft: #ccfbf1;
  --accent-deep: #134e4a;
  --accent-border: #99f6e4;
  --accent-rgb: 15, 118, 110;
  --bg-1: #f0fdfa;
  --bg-2: #f7fffc;
  --bg-glow-1: #99f6e4;
  --bg-glow-2: #ccfbf1;
  --border: #d5f5f0;
}

[data-topic="stability-differential-equations"] {
  --accent: #0e7490;
  --accent-2: #06b6d4;
  --accent-3: #67e8f9;
  --accent-soft: #cffafe;
  --accent-deep: #164e63;
  --accent-border: #a5f3fc;
  --accent-rgb: 14, 116, 144;
  --bg-1: #ecfeff;
  --bg-2: #f5fcff;
  --bg-glow-1: #a5f3fc;
  --bg-glow-2: #cffafe;
  --border: #d5f5f6;
}

[data-topic="complex-numbers"] {
  --accent: #0284c7;
  --accent-2: #38bdf8;
  --accent-3: #7dd3fc;
  --accent-soft: #e0f2fe;
  --accent-deep: #0369a1;
  --accent-border: #bae6fd;
  --accent-rgb: 2, 132, 199;
  --bg-1: #eef8fc;
  --bg-2: #f5fbff;
  --bg-glow-1: #bae6fd;
  --bg-glow-2: #e0f2fe;
  --border: #e2eef5;
}

[data-topic="calculus"] {
  --accent: #1d4ed8;
  --accent-2: #60a5fa;
  --accent-3: #93c5fd;
  --accent-soft: #dbeafe;
  --accent-deep: #1e40af;
  --accent-border: #bfdbfe;
  --accent-rgb: 29, 78, 216;
  --bg-1: #eff6ff;
  --bg-2: #f8fbff;
  --bg-glow-1: #bfdbfe;
  --bg-glow-2: #dbeafe;
  --border: #e0e7ff;
}

[data-topic="integrals"] {
  --accent: #0f766e;
  --accent-2: #2dd4bf;
  --accent-3: #5eead4;
  --accent-soft: #ccfbf1;
  --accent-deep: #115e59;
  --accent-border: #99f6e4;
  --accent-rgb: 15, 118, 110;
  --bg-1: #f0fdfa;
  --bg-2: #f7fffc;
  --bg-glow-1: #99f6e4;
  --bg-glow-2: #ccfbf1;
  --border: #d5f5f0;
}

[data-topic="definite-integrals"] {
  --accent: #1e40af;
  --accent-2: #3b82f6;
  --accent-3: #93c5fd;
  --accent-soft: #dbeafe;
  --accent-deep: #1e3a8a;
  --accent-border: #bfdbfe;
  --accent-rgb: 30, 64, 175;
  --bg-1: #eff6ff;
  --bg-2: #f8fbff;
  --bg-glow-1: #bfdbfe;
  --bg-glow-2: #dbeafe;
  --border: #dde7f8;
}

[data-topic="applications-of-definite-integrals"] {
  --accent: #4338ca;
  --accent-2: #818cf8;
  --accent-3: #c7d2fe;
  --accent-soft: #eef2ff;
  --accent-deep: #312e81;
  --accent-border: #c7d2fe;
  --accent-rgb: 67, 56, 202;
  --bg-1: #eef2ff;
  --bg-2: #f8faff;
  --bg-glow-1: #c7d2fe;
  --bg-glow-2: #e0e7ff;
  --border: #e0e7ff;
}

[data-topic="double-integrals"] {
  --accent: #0c4a6e;
  --accent-2: #0ea5e9;
  --accent-3: #7dd3fc;
  --accent-soft: #e0f2fe;
  --accent-deep: #075985;
  --accent-border: #bae6fd;
  --accent-rgb: 12, 74, 110;
  --bg-1: #f0f9ff;
  --bg-2: #f8fcff;
  --bg-glow-1: #bae6fd;
  --bg-glow-2: #e0f2fe;
  --border: #d6eaf5;
}

[data-topic="differential-calculus"] {
  --accent: #1d4ed8;
  --accent-2: #38bdf8;
  --accent-3: #7dd3fc;
  --accent-soft: #e0f2fe;
  --accent-deep: #1e3a8a;
  --accent-border: #bae6fd;
  --accent-rgb: 29, 78, 216;
  --bg-1: #f0f7ff;
  --bg-2: #f7fbff;
  --bg-glow-1: #bfdbfe;
  --bg-glow-2: #e0f2fe;
  --border: #dce8f6;
}

[data-topic="series"] {
  --accent: #0369a1;
  --accent-2: #38bdf8;
  --accent-3: #7dd3fc;
  --accent-soft: #e0f2fe;
  --accent-deep: #0c4a6e;
  --accent-border: #bae6fd;
  --accent-rgb: 3, 105, 161;
  --bg-1: #f0f9ff;
  --bg-2: #f7fcff;
  --bg-glow-1: #bae6fd;
  --bg-glow-2: #e0f2fe;
  --border: #d6eaf5;
}

[data-topic="limits"] {
  --accent: #1e3a8a;
  --accent-2: #60a5fa;
  --accent-3: #93c5fd;
  --accent-soft: #dbeafe;
  --accent-deep: #172554;
  --accent-border: #bfdbfe;
  --accent-rgb: 30, 58, 138;
  --bg-1: #eff6ff;
  --bg-2: #f8fbff;
  --bg-glow-1: #bfdbfe;
  --bg-glow-2: #dbeafe;
  --border: #dde7f8;
}

[data-topic="probability"] {
  --accent: #0e7490;
  --accent-2: #22d3ee;
  --accent-3: #67e8f9;
  --accent-soft: #cffafe;
  --accent-deep: #155e75;
  --accent-border: #a5f3fc;
  --accent-rgb: 14, 116, 144;
  --bg-1: #ecfeff;
  --bg-2: #f5fcff;
  --bg-glow-1: #a5f3fc;
  --bg-glow-2: #cffafe;
  --border: #d5f5f6;
}

[data-topic="geometry"] {
  --accent: #0f766e;
  --accent-2: #2dd4bf;
  --accent-3: #5eead4;
  --accent-soft: #ccfbf1;
  --accent-deep: #115e59;
  --accent-border: #99f6e4;
  --accent-rgb: 15, 118, 110;
  --bg-1: #f0fdfa;
  --bg-2: #f7fffc;
  --bg-glow-1: #99f6e4;
  --bg-glow-2: #ccfbf1;
  --border: #d5f5f0;
}

[data-topic="physics"] {
  --accent: #4f46e5;
  --accent-2: #818cf8;
  --accent-3: #a5b4fc;
  --accent-soft: #e0e7ff;
  --accent-deep: #312e81;
  --accent-border: #c7d2fe;
  --accent-rgb: 79, 70, 229;
  --bg-1: #eef2ff;
  --bg-2: #f8f9ff;
  --bg-glow-1: #c7d2fe;
  --bg-glow-2: #e0e7ff;
  --border: #dde3fb;
}


[data-topic="modeling-and-simulations"] {
  --accent: #b45309;
  --accent-2: #f59e0b;
  --accent-3: #fbbf24;
  --accent-soft: #fef3c7;
  --accent-deep: #7c2d12;
  --accent-border: #fcd34d;
  --accent-rgb: 180, 83, 9;
  --bg-1: #fffbeb;
  --bg-2: #fffdf7;
  --bg-glow-1: #fde68a;
  --bg-glow-2: #fef3c7;
  --border: #fde8c8;
}
[data-topic="partial-differential-equations"] {
  --accent: #1e40af;
  --accent-2: #38bdf8;
  --accent-3: #7dd3fc;
  --accent-soft: #e0f2fe;
  --accent-deep: #1e3a8a;
  --accent-border: #bae6fd;
  --accent-rgb: 30, 64, 175;
  --bg-1: #eff6ff;
  --bg-2: #f8fbff;
  --bg-glow-1: #bfdbfe;
  --bg-glow-2: #e0f2fe;
  --border: #dde7f8;
}

@media (prefers-color-scheme: dark) {
  html:not([data-theme="light"]) {
    color-scheme: dark;
    --bg-1: #0b1220;
    --bg-2: #111827;
    --bg-glow-1: rgba(var(--accent-rgb), 0.28);
    --bg-glow-2: rgba(var(--accent-rgb), 0.12);
    --card-bg: #1a2333;
    --text: #e8eef6;
    --lead: #c5d0dc;
    --muted: #9aa8bc;
    --border: #2c3b50;
    --accent-soft: rgba(var(--accent-rgb), 0.18);
    --accent-border: rgba(var(--accent-rgb), 0.42);
    --accent-deep: color-mix(in srgb, var(--accent-2) 70%, #fff);
    --green: #4ade80;
    --green-soft: rgba(74, 222, 128, 0.14);
    --method-bg: rgba(var(--accent-rgb), 0.14);
    --remark-bg: rgba(20, 184, 166, 0.12);
    --remark-border: rgba(45, 212, 191, 0.35);
    --result-border: rgba(74, 222, 128, 0.4);
    --warn: #fbbf24;
    --warn-bar: #f59e0b;
    --surface-2: rgba(255, 255, 255, 0.04);
    --domain-bg: rgba(var(--accent-rgb), 0.16);
    --crumb-sep: #4b5c70;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.35);
    --shadow-lg: 0 20px 45px -18px rgba(0, 0, 0, 0.5),
      0 8px 20px -8px rgba(0, 0, 0, 0.35);
  }
}

html[data-theme="dark"] {
  color-scheme: dark;
  --bg-1: #0b1220;
  --bg-2: #111827;
  --bg-glow-1: rgba(var(--accent-rgb), 0.28);
  --bg-glow-2: rgba(var(--accent-rgb), 0.12);
  --card-bg: #1a2333;
  --text: #e8eef6;
  --lead: #c5d0dc;
  --muted: #9aa8bc;
  --border: #2c3b50;
  --accent-soft: rgba(var(--accent-rgb), 0.18);
  --accent-border: rgba(var(--accent-rgb), 0.42);
  --accent-deep: color-mix(in srgb, var(--accent-2) 70%, #fff);
  --green: #4ade80;
  --green-soft: rgba(74, 222, 128, 0.14);
  --method-bg: rgba(var(--accent-rgb), 0.14);
  --remark-bg: rgba(20, 184, 166, 0.12);
  --remark-border: rgba(45, 212, 191, 0.35);
  --result-border: rgba(74, 222, 128, 0.4);
  --warn: #fbbf24;
  --warn-bar: #f59e0b;
  --surface-2: rgba(255, 255, 255, 0.04);
  --domain-bg: rgba(var(--accent-rgb), 0.16);
  --crumb-sep: #4b5c70;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 20px 45px -18px rgba(0, 0, 0, 0.5),
    0 8px 20px -8px rgba(0, 0, 0, 0.35);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  color-scheme: light;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(1000px 500px at 15% -10%, var(--bg-glow-1) 0%, transparent 60%),
    radial-gradient(900px 500px at 100% 10%, var(--bg-glow-2) 0%, transparent 55%),
    linear-gradient(180deg, var(--bg-1), var(--bg-2));
  font-family: "Inter", system-ui, -apple-system, sans-serif;
  color: var(--text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

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

mjx-container,
mjx-container mjx-math,
mjx-container mjx-c {
  color: inherit;
  -webkit-text-fill-color: currentColor;
}

.page-shell {
  max-width: var(--max);
  margin: 0 auto;
  padding: 28px 20px 64px;
}

.top-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 36px;
  animation: rise 0.45s ease-out;
}

.brand {
  font-weight: 800;
  font-size: 1.05rem;
  letter-spacing: -0.02em;
  color: var(--accent-deep);
  background-image: linear-gradient(135deg, var(--accent), var(--accent-3));
  -webkit-background-clip: text;
  background-clip: text;
}

.nav-links {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
  align-items: center;
}

.nav-links a {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--muted);
  transition: color 0.15s ease;
}

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

.nav-links a[aria-current="page"] {
  color: var(--accent-deep);
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  margin-left: 2px;
  padding: 0;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--card-bg);
  color: var(--text);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: background 0.15s ease, border-color 0.15s ease, transform 0.15s ease;
}

.theme-toggle:hover {
  border-color: var(--accent-border);
  color: var(--accent-deep);
  transform: translateY(-1px);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
}

.page-shell:has(.crumbs) .top-nav {
  margin-bottom: 14px;
}

.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin: 0 0 28px;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--muted);
  animation: rise 0.45s ease-out;
}

.crumbs a {
  color: var(--muted);
  transition: color 0.15s ease;
}

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

.crumbs [aria-current="page"] {
  color: var(--text);
}

.crumbs-sep {
  color: var(--crumb-sep);
  font-weight: 500;
}

.home-hero,
.topic-hero {
  margin-bottom: 40px;
  animation: rise 0.5s ease-out;
}

.home-hero {
  margin-bottom: 28px;
}

.brand-hero {
  margin: 0 0 14px;
  font-size: clamp(2.4rem, 6vw, 3.4rem);
  font-weight: 800;
  letter-spacing: -0.035em;
  line-height: 1.1;
  color: var(--accent-deep);
  background-image: linear-gradient(135deg, var(--accent), var(--accent-2), var(--accent-3));
  -webkit-background-clip: text;
  background-clip: text;
}

.topic-hero h1 {
  margin: 0 0 12px;
  font-size: clamp(1.8rem, 4vw, 2.4rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--accent-deep);
  background-image: linear-gradient(135deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
}

@supports ((-webkit-background-clip: text) or (background-clip: text)) {
  .brand,
  .brand-hero,
  .topic-hero h1 {
    color: transparent;
    -webkit-text-fill-color: transparent;
  }
}

html[data-theme="dark"] .brand,
html[data-theme="dark"] .brand-hero,
html[data-theme="dark"] .topic-hero h1 {
  color: var(--accent-2);
  background-image: linear-gradient(135deg, var(--accent-2), var(--accent-3));
}

@media (prefers-color-scheme: dark) {
  html:not([data-theme="light"]) .brand,
  html:not([data-theme="light"]) .brand-hero,
  html:not([data-theme="light"]) .topic-hero h1 {
    color: var(--accent-2);
    background-image: linear-gradient(135deg, var(--accent-2), var(--accent-3));
  }
}

.lead {
  margin: 0;
  max-width: none;
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--lead);
}

.topic-intro {
  margin: -12px 0 32px;
}

.topic-intro-meta {
  margin: 0 0 16px;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--muted);
}

.topic-intro-meta strong {
  color: var(--text);
  font-weight: 800;
}

.topic-intro-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.topic-intro-actions .btn-secondary {
  text-decoration: none;
}

.topic-intro-actions [hidden],
.chapter-index[hidden],
.chapter-pills[hidden] {
  display: none !important;
}

.topic-list-panel {
  position: relative;
}

.topic-loading {
  margin: 0 0 22px;
}

.topic-loading-label {
  margin: 0 0 14px;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--muted);
}

.topic-skeleton {
  display: grid;
  gap: 22px;
}

.topic-skeleton-card {
  height: 168px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: linear-gradient(
    90deg,
    var(--card-bg) 0%,
    var(--bg-2) 40%,
    var(--card-bg) 80%
  );
  background-size: 200% 100%;
  animation: topic-skeleton-shimmer 1.2s ease-in-out infinite;
}

.topic-list-panel.is-loading .topic-loading {
  position: absolute;
  inset: 0;
  z-index: 1;
  margin: 0;
  padding: 4px 0 0;
  background: var(--bg-1);
}

.topic-list-panel.is-loading .statement-list {
  visibility: hidden;
}

.statement-list:not(.is-ready):has(.statement-card)::before {
  content: "Loading problems…";
  display: block;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--muted);
  padding: 8px 2px 4px;
}

.topic-list-panel.is-waiting .statement-list:not(.is-ready)::before,
.statement-list.is-ready::before {
  content: none;
  display: none;
}

@keyframes topic-skeleton-shimmer {
  0% {
    background-position: 100% 0;
  }
  100% {
    background-position: -100% 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  .topic-skeleton-card {
    animation: none;
  }
}

.home-hero .lead {
  max-width: none;
  font-size: 1.12rem;
  line-height: 1.7;
  color: var(--muted);
}

.home-hero .lead + .lead {
  margin-top: 12px;
}

.home-hero .lead a {
  color: var(--accent);
  font-weight: 700;
}

.home-hero .lead a:hover {
  color: var(--accent-deep);
}

.home-welcome {
  max-width: none;
  margin: 18px 0 0;
}

.home-welcome p {
  margin: 0 0 12px;
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--lead);
}

.home-welcome p:last-child {
  margin-bottom: 0;
}

.home-welcome a {
  color: var(--accent);
  font-weight: 700;
}

.home-welcome a:hover {
  color: var(--accent-deep);
}

.topic-guide {
  max-width: none;
  margin: 18px 0 0;
}

.topic-guide p {
  margin: 0 0 12px;
  font-size: 1.02rem;
  line-height: 1.75;
  color: var(--lead);
}

.topic-guide p:last-child {
  margin-bottom: 0;
}

.topic-guide a {
  color: var(--accent);
  font-weight: 700;
}

.topic-guide a:hover {
  color: var(--accent-deep);
}

.home-welcome-luck {
  font-weight: 700;
  color: var(--accent-deep);
}

.about-hero .lead {
  max-width: none;
}

.about-hero .lead + .lead {
  margin-top: 12px;
}

.about-story {
  display: flex;
  flex-direction: column;
  gap: 18px;
  animation: rise 0.55s ease-out;
}

.about-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 28px 30px 30px;
}

.about-card h2 {
  margin: 0 0 12px;
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text);
}

.about-card p {
  margin: 0 0 12px;
  font-size: 1.02rem;
  line-height: 1.7;
  color: var(--lead);
}

.about-card p:last-child {
  margin-bottom: 0;
}

.about-card a {
  color: var(--accent);
  font-weight: 700;
}

.about-card a:hover {
  color: var(--accent-deep);
}

.about-card ul {
  margin: 0 0 12px;
  padding-left: 22px;
}

.about-card ul:last-child {
  margin-bottom: 0;
}

.about-card li {
  margin: 6px 0;
  font-size: 1.02rem;
  line-height: 1.7;
  color: var(--lead);
}

.about-card code {
  font-size: 0.88em;
  background: var(--accent-soft);
  color: var(--accent-deep);
  padding: 1px 6px;
  border-radius: 6px;
}

.topic-hero:has(+ .home-how) {
  margin-bottom: 18px;
}

.home-how {
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin: 0 0 36px;
}

.home-how-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 22px 24px 24px;
}

.home-how-card h2 {
  margin: 0 0 10px;
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text);
}

.home-how-card p {
  margin: 0 0 12px;
  font-size: 1.02rem;
  line-height: 1.7;
  color: var(--lead);
}

.home-how-card p:last-child {
  margin-bottom: 0;
}

.home-how-card a {
  color: var(--accent);
  font-weight: 700;
}

.home-how-card a:hover {
  color: var(--accent-deep);
}

.home-stats {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 18px 0 0;
}

.topic-jump {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 16px 0 0;
}

.topic-jump a {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  padding: 5px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--card-bg);
  color: var(--text);
  font-size: 0.8rem;
  font-weight: 700;
  text-decoration: none;
  box-shadow: var(--shadow-sm);
}

.topic-jump a:hover,
.topic-jump a:focus-visible {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-deep);
}

.home-stat {
  display: inline-flex;
  align-items: baseline;
  gap: 7px;
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--muted);
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 8px 16px;
  box-shadow: var(--shadow-sm);
}

.home-stat strong {
  font-size: 1.12rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--accent-deep);
}

a.home-stat:hover,
a.home-stat:focus-visible {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-deep);
}

.topics-catalog {
  display: flex;
  flex-direction: column;
  gap: 28px;
  animation: rise 0.55s ease-out;
}

.topic-groups-row {
  display: grid;
  gap: 28px 14px;
}

.topic-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
  scroll-margin-top: 88px;
}

.topic-group-title {
  margin: 0 4px;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  scroll-margin-top: 88px;
}

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

.topic-groups-row .topics-grid {
  grid-template-columns: 1fr;
}

.topic-card {
  position: relative;
  display: flex;
  flex-direction: column;
  height: 100%;
  min-width: 0;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  color: inherit;
  text-decoration: none;
  transition: transform 0.2s ease, box-shadow 0.2s ease, opacity 0.2s ease;
}

.topic-thumb {
  display: block;
  background: color-mix(in srgb, var(--accent) 10%, var(--card-bg));
  border-bottom: 1px solid var(--border);
}

.topic-fig {
  display: block;
  width: 100%;
  height: 112px;
}

.topic-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 24px 50px -16px rgba(var(--accent-rgb), 0.22),
    0 10px 24px -10px rgba(30, 34, 51, 0.1);
}

.topic-card-accent {
  height: 4px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--accent-3));
}

.topic-card-body {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 6px;
  flex: 1;
  padding: 14px 16px 16px;
}

.topic-card-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 8px 12px;
  flex-wrap: wrap;
  margin: 0;
}

.topic-card-head h3 {
  margin: 0;
  min-width: 0;
  flex: 1 1 8rem;
  padding-right: 0;
}

.topic-card-head .topic-count {
  margin: 0;
  flex: none;
  white-space: nowrap;
}

.topic-card-icon {
  display: none;
}

.topic-card-icon svg {
  width: 24px;
  height: 24px;
}

.topic-card-body h3 {
  padding-right: 0;
}

.topic-card.is-empty .topic-card-icon {
  color: var(--muted);
  background: var(--bg-2);
  border-color: var(--border);
}

.topic-hero-title {
  display: flex;
  align-items: center;
  gap: 14px;
  margin: 0 0 12px;
}

.topic-hero-icon {
  flex: none;
  width: 48px;
  height: 48px;
  display: grid;
  place-items: center;
  border-radius: 14px;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
}

.topic-hero-icon svg {
  width: 26px;
  height: 26px;
}

.topic-hero-title h1 {
  margin: 0;
}

.topic-count {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
  border-radius: 999px;
  padding: 3px 9px;
  margin-bottom: 0;
}

.topic-card h2,
.topic-card h3 {
  margin: 0;
  font-size: 1.05rem;
  font-weight: 800;
  letter-spacing: -0.015em;
  line-height: 1.25;
}

.topic-card.is-empty {
  opacity: 0.72;
  box-shadow: var(--shadow-sm);
}

.topic-card.is-empty:hover {
  opacity: 1;
}

.topic-card.is-empty .topic-card-accent {
  opacity: 0.4;
}

.topic-card.is-empty .topic-count {
  color: var(--muted);
  background: var(--bg-2);
  border-color: var(--border);
}

.topic-card.is-empty .topic-cta {
  color: var(--muted);
}

.topic-card p {
  margin: 0;
  color: var(--lead);
  font-size: 0.9rem;
  line-height: 1.45;
}

.topic-card .topic-cta {
  display: none;
}

.topic-cta {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--accent);
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin: 0 auto 18px;
  max-width: 760px;
  width: 100%;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--muted);
  transition: color 0.15s ease;
}

.page-shell > .back-link {
  display: flex;
}

.back-link:hover {
  color: var(--accent);
}

.topic-search {
  margin: 0 0 22px;
  padding: 22px 24px 24px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.topic-search label {
  display: block;
  margin-bottom: 10px;
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--text);
}

.topic-search-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.topic-search input,
.topic-search select,
.topic-search .app-select {
  flex: 1 1 160px;
  min-width: 0;
}

.topic-search input,
.topic-search select,
.test-field select {
  appearance: none;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  font-family: inherit;
  font-size: 0.98rem;
  font-weight: 600;
  color: var(--text);
}

.topic-search input {
  flex: 2 1 220px;
}

.topic-search select,
.test-field select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%236b7280' stroke-width='2.2'%3E%3Cpath d='M6 9l6 6 6-6' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  background-size: 16px;
  padding-right: 38px;
  cursor: pointer;
}

html[data-theme="dark"] .topic-search select,
html[data-theme="dark"] .test-field select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%239aa8bc' stroke-width='2.2'%3E%3Cpath d='M6 9l6 6 6-6' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
}

@media (prefers-color-scheme: dark) {
  html:not([data-theme="light"]) .topic-search select,
  html:not([data-theme="light"]) .test-field select {
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%239aa8bc' stroke-width='2.2'%3E%3Cpath d='M6 9l6 6 6-6' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  }
}

.topic-search input:focus,
.topic-search select:focus,
.test-field select:focus,
.app-select-trigger:focus {
  outline: 2px solid var(--accent-border);
  border-color: var(--accent);
}

.app-select {
  position: relative;
}

.test-field .app-select {
  width: 100%;
}

.app-select > select {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
  pointer-events: none;
}

.app-select-trigger {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  width: 100%;
  appearance: none;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 12px 12px 14px;
  font-family: inherit;
  font-size: 0.98rem;
  font-weight: 600;
  color: var(--text);
  text-align: left;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.app-select-trigger:hover {
  border-color: var(--accent-border);
  background: var(--card-bg);
}

.app-select.is-open .app-select-trigger {
  border-color: var(--accent);
  outline: 2px solid var(--accent-border);
}

.app-select.is-invalid .app-select-trigger,
.app-select.is-invalid .app-select-trigger:focus {
  border-color: #dc2626;
  outline-color: #fecaca;
}

.app-select-trigger.is-placeholder .app-select-value {
  color: var(--muted);
}

.app-select-value {
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.app-select-chevron {
  flex: none;
  color: var(--muted);
  transition: transform 0.15s ease;
}

.app-select.is-open .app-select-chevron {
  transform: rotate(180deg);
  color: var(--accent);
}

@media (prefers-reduced-motion: reduce) {
  .app-select-trigger,
  .app-select-chevron,
  .app-select-option {
    transition: none;
  }
}

.app-select-menu {
  position: absolute;
  z-index: 30;
  top: calc(100% + 6px);
  left: 0;
  right: auto;
  width: max-content;
  min-width: 100%;
  max-width: max(100%, min(24rem, calc(100vw - 32px)));
  max-height: min(320px, 60vh);
  overflow: auto;
  overscroll-behavior: contain;
  padding: 6px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: var(--shadow-lg);
}

.app-select-group + .app-select-option,
.app-select-group + .app-select-group {
  margin-top: 4px;
}

.app-select-group-label {
  padding: 8px 10px 4px;
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-deep);
}

.app-select-group .app-select-option {
  padding-left: 14px;
}

.app-select-option {
  display: block;
  padding: 10px 12px;
  border-radius: 10px;
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
  white-space: normal;
  transition: background 0.12s ease, color 0.12s ease;
}

.app-select-option.is-active:not(.is-selected) {
  background: var(--accent-soft);
  color: var(--accent-deep);
}

.app-select-option.is-selected {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #fff;
}

.app-select-option.is-disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.topic-search input.is-invalid {
  border-color: #dc2626;
}

.topic-search input.is-invalid:focus {
  outline-color: #fecaca;
  border-color: #dc2626;
}

.topic-search .btn-primary {
  flex: 0 0 auto;
}

.topic-search-error {
  margin: 10px 0 0;
  font-size: 0.86rem;
  font-weight: 600;
  color: #dc2626;
}

.chapter-heading {
  margin: 8px 4px 0;
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-deep);
}

.chapter-index {
  margin: 0 0 28px;
}

.chapter-index-title {
  margin: 0 0 8px;
  font-size: 1.35rem;
  font-weight: 800;
  letter-spacing: -0.02em;
}

.chapter-index-lead {
  margin: 0 0 20px;
  font-size: 0.98rem;
  line-height: 1.6;
  color: var(--lead);
}

.chapter-index-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.chapter-index-card {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 18px 20px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  text-decoration: none;
  color: inherit;
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease;
}

.chapter-index-card:hover {
  transform: translateY(-2px);
  border-color: var(--accent-border);
  box-shadow: 0 18px 36px -16px rgba(var(--accent-rgb), 0.22),
    0 8px 18px -10px rgba(30, 34, 51, 0.08);
}

.chapter-index-card.is-empty {
  opacity: 0.5;
  pointer-events: none;
}

.chapter-index-num {
  flex: none;
  width: 36px;
  height: 36px;
  display: grid;
  place-items: center;
  border-radius: 10px;
  font-size: 0.88rem;
  font-weight: 800;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
}

.chapter-index-body {
  flex: 1 1 auto;
  min-width: 0;
  display: grid;
  gap: 4px;
}

.chapter-index-name {
  font-size: 1.02rem;
  font-weight: 800;
  letter-spacing: -0.015em;
  line-height: 1.3;
}

.chapter-index-meta {
  font-size: 0.86rem;
  font-weight: 600;
  color: var(--muted);
}

.chapter-index-go {
  flex: none;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--accent-deep);
}

.chapter-index-all {
  margin: 18px 4px 0;
  font-size: 0.92rem;
  font-weight: 600;
}

.chapter-index-all a {
  color: var(--accent-deep);
}

.chapter-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0 0 22px;
}

.chapter-pills a {
  display: inline-flex;
  align-items: center;
  min-height: 36px;
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg-2);
  color: var(--text);
  font-size: 0.82rem;
  font-weight: 700;
  text-decoration: none;
}

.chapter-pills a:hover,
.chapter-pills a.is-active {
  border-color: var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-deep);
}

.topic-search.is-chapter-first .app-select:has(#topic-chapter-filter),
.topic-search.is-chapter-first #topic-chapter-filter {
  display: none !important;
}

.topic-search.is-index .app-select:has(#topic-page-size),
.topic-search.is-index #topic-page-size {
  display: none !important;
}

.statement-list {
  display: grid;
  gap: 22px;
}

.statement-list .statement-card {
  display: none;
}

.statement-list .statement-card.is-visible {
  display: block;
}

.statement-card {
  position: relative;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  padding: 32px 34px 34px;
  overflow: hidden;
  animation: rise 0.5s ease-out;
}

.statement-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 6px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--accent-3));
}

.statement-card-top {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: 8px;
  margin-bottom: 14px;
}

.statement-card h2 {
  margin: 0 0 18px;
  font-size: 1.2rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  line-height: 1.4;
}

.statement-preview {
  margin: 0 0 24px !important;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 0;
  cursor: pointer;
  font-family: inherit;
  font-size: 0.92rem;
  font-weight: 700;
  color: #fff;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  padding: 11px 18px;
  border-radius: 12px;
  box-shadow: 0 4px 12px -3px rgba(var(--accent-rgb), 0.45);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 18px -4px rgba(var(--accent-rgb), 0.5);
}

.pagination {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 28px;
}

.pagination-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 40px;
  height: 40px;
  padding: 0 12px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card-bg);
  color: var(--text);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.pagination-btn:not(.pagination-num) {
  min-width: auto;
  padding: 0 14px;
}

.pagination-btn:hover:not(:disabled):not(.is-active) {
  border-color: var(--accent-border);
  color: var(--accent);
  background: var(--accent-soft);
}

.pagination-btn.is-active {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-color: transparent;
  color: #fff;
  cursor: default;
}

.pagination-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.pagination-meta {
  width: 100%;
  text-align: center;
  margin-top: 4px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--muted);
}

.pagination-jump {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-left: 6px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--muted);
}

.pagination-jump input {
  width: 64px;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card-bg);
  padding: 0 10px;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--text);
}

.pagination-jump input:focus {
  outline: 2px solid var(--accent-border);
  border-color: var(--accent);
}

/* Create test */
.test-builder {
  margin-bottom: 36px;
  animation: rise 0.5s ease-out;
}

.test-form {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  padding: 28px 30px 30px;
  display: grid;
  gap: 22px;
}

.test-field label,
.test-field legend {
  display: block;
  margin-bottom: 10px;
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--text);
}

.test-field select {
  width: 100%;
}

.test-field select.is-invalid {
  border-color: #dc2626;
}

.test-field select.is-invalid:focus {
  outline-color: #fecaca;
  border-color: #dc2626;
}

.test-field-error {
  margin: 8px 0 0;
  font-size: 0.86rem;
  font-weight: 600;
  color: #dc2626;
}

.test-field-hint {
  margin-left: 8px;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0;
  text-transform: none;
  color: var(--muted);
}

.test-topic-groups {
  display: grid;
  gap: 16px;
}

.test-topic-group-title {
  margin: 0 0 8px;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
}

.test-topic-options {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
}

.test-topic-option span {
  width: 100%;
  min-width: 0;
  height: auto;
  min-height: 44px;
  justify-content: flex-start;
  text-align: left;
  padding: 10px 14px;
  font-size: 0.9rem;
  line-height: 1.3;
}

.test-topics.is-invalid .test-topic-option span {
  border-color: #fecaca;
}

@media (max-width: 720px) {
  .test-topic-options {
    grid-template-columns: 1fr;
  }
}

.test-topics,
.test-count {
  margin: 0;
  padding: 0;
  border: 0;
  min-width: 0;
}

.test-count-options {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.test-count-option {
  position: relative;
  cursor: pointer;
}

.test-count-option input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.test-count-option span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 56px;
  height: 44px;
  padding: 0 16px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--bg-2);
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.test-count-option input:checked + span {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-color: transparent;
  color: #fff;
}

.test-count-option input:focus-visible + span {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.test-count-option.is-disabled {
  cursor: not-allowed;
  opacity: 0.4;
}

.test-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: inherit;
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--accent-deep);
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
  padding: 11px 18px;
  border-radius: 12px;
  cursor: pointer;
  transition: background 0.15s ease, transform 0.15s ease;
}

.btn-secondary:hover {
  transform: translateY(-1px);
  background: var(--card-bg);
}

.test-hint {
  margin: 0;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--muted);
}

.test-results {
  animation: rise 0.45s ease-out;
}

.test-results-head {
  margin-bottom: 22px;
}

.test-results-head h2 {
  margin: 0 0 6px;
  font-size: 1.35rem;
  font-weight: 800;
  letter-spacing: -0.015em;
}

.test-results-meta {
  margin: 0;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--muted);
}

.test-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 16px;
}

.test-progress {
  position: sticky;
  top: 10px;
  z-index: 8;
  margin: 0 0 20px;
  padding: 12px 16px 14px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow-sm);
}

.test-progress-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
  font-size: 0.88rem;
  font-weight: 700;
}

#test-progress-label {
  color: var(--text);
}

#test-progress-attempted {
  color: var(--muted);
  font-weight: 600;
  font-size: 0.82rem;
}

.test-progress-track {
  height: 4px;
  margin-top: 10px;
  background: var(--accent-soft);
  border-radius: 999px;
  overflow: hidden;
}

.test-progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border-radius: inherit;
  transition: width 0.2s ease;
}

.test-item-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

.test-view-solution {
  display: none;
}

.test-attempted-label {
  display: none;
  align-items: center;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--green);
}

.test-item.is-attempted .test-attempt-btn {
  display: none;
}

.test-item.is-attempted .test-attempted-label {
  display: inline-flex;
}

.test-item.is-attempted .test-view-solution,
.test-results.is-done .test-view-solution {
  display: inline-flex;
}

.test-results.is-done .test-attempt-btn {
  display: none;
}

.test-end-actions {
  margin-top: 28px;
}

.exam-back-bar {
  margin: 0 0 14px;
}

.exam-back-bar .btn-primary {
  text-decoration: none;
}

.print-only {
  display: none !important;
}

.test-print-header {
  margin: 0 0 22px;
}

.test-print-kicker {
  margin: 0 0 2px;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  text-align: center;
}

.test-print-header h1 {
  margin: 0;
  font-size: 1.45rem;
  font-weight: 700;
  letter-spacing: 0;
  text-align: center;
}

.test-print-count {
  margin: 4px 0 0;
  text-align: center;
}

.test-print-id {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(0, 0.8fr);
  gap: 18px 28px;
  margin: 16px 0 10px;
}

.test-print-id > div {
  display: flex;
  align-items: baseline;
  gap: 8px;
  min-width: 0;
}

.test-print-id span:first-child {
  flex: none;
  font-size: 0.92rem;
  font-weight: 600;
}

.test-print-line {
  flex: 1;
  min-width: 0;
  border-bottom: 1px solid currentColor;
  height: 1.15em;
}

.test-print-note {
  margin: 0;
  font-size: 0.92rem;
}

.test-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  width: 100%;
  gap: 22px;
  counter-reset: none;
}

.test-item,
.test-card {
  width: 100%;
  max-width: 100%;
  min-width: 0;
}

.test-card .problem-statement {
  max-width: 100%;
  overflow-x: auto;
}

.test-item {
  margin: 0;
  scroll-margin-top: 84px;
}

.test-card h3 {
  margin: 0 0 18px;
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  line-height: 1.4;
}

.test-card .statement-preview {
  margin-bottom: 18px !important;
}

.blog-kicker {
  margin: 0 0 8px;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.blog-groups {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

.blog-series h2 {
  margin: 0 0 10px;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.blog-series-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 14px;
}

.blog-card {
  display: flex;
  flex-direction: column;
  height: 100%;
  min-width: 0;
  padding: 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card-bg);
  box-shadow: var(--shadow-sm);
  color: inherit;
  text-decoration: none;
  overflow: hidden;
}

.blog-card:hover {
  border-color: var(--accent);
  background: var(--card-bg);
}

.blog-thumb {
  position: relative;
  display: block;
  background: color-mix(in srgb, var(--accent) 9%, var(--card-bg));
  border-bottom: 1px solid var(--border);
}

.blog-fig {
  display: block;
  width: 100%;
  height: 118px;
}

.blog-part {
  position: absolute;
  top: 8px;
  left: 8px;
  min-width: 1.6rem;
  height: 1.6rem;
  padding: 0 6px;
  display: grid;
  place-items: center;
  border-radius: 999px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  font-size: 0.75rem;
  font-weight: 800;
  line-height: 1;
  color: var(--accent);
}

.blog-card-body {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 12px 14px 14px;
}

.blog-card h3 {
  margin: 0;
  font-size: 1.02rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.35;
  color: var(--text);
}

.blog-card p {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.45;
  color: var(--lead);
}

.blog-search {
  margin-bottom: 22px;
}

.blog-front {
  margin-bottom: 28px;
}

.blog-jump {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0 0 28px;
}

.blog-jump a {
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--card-bg);
  color: var(--text);
  font-size: 0.84rem;
  font-weight: 700;
  line-height: 1.3;
  text-decoration: none;
}

.blog-jump a:hover {
  background: var(--accent-soft);
  color: var(--accent);
}

.blog-latest h2 {
  margin: 0 0 10px;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.blog-series h2 {
  scroll-margin-top: 16px;
}

.blog-search-status {
  margin: 12px 0 0;
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--lead);
}

.blog-card mark {
  background: var(--accent-soft);
  color: var(--text);
  font-weight: 700;
  padding: 0 0.12em;
  border-radius: 4px;
}

.blog-groups.is-searching .blog-series-list {
  display: grid;
}

.blog-post {
  --vec-a: var(--accent);
  --vec-b: var(--green);
  --vec-c: #dc2626;
  max-width: 100%;
  overflow-x: auto;
  font-size: 1.05rem;
  line-height: 1.75;
  color: var(--lead);
}

html[data-theme="dark"] .blog-post,
html:not([data-theme="light"]) .blog-post {
  --vec-c: #ff8b84;
}

html[data-theme="light"] .blog-post {
  --vec-c: #dc2626;
}

.blog-post h2 {
  margin: 2.2em 0 0.55em;
  padding-bottom: 0.3em;
  border-bottom: 1px solid var(--border);
  font-size: 1.35rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text);
}

.blog-post h3 {
  margin: 1.6em 0 0.4em;
  font-size: 1.08rem;
  font-weight: 800;
  color: var(--text);
}

.blog-post p {
  margin: 0 0 1em;
}

.blog-post a {
  color: var(--accent);
  font-weight: 700;
}

.blog-post a:hover {
  color: var(--accent-deep);
}

.blog-post .toc {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 16px 22px 18px;
  margin: 0 0 8px;
}

.blog-post .toc ol {
  margin: 0.4em 0 0;
  padding-left: 1.2em;
}

.blog-post .toc li {
  margin: 0.25em 0;
}

.blog-post .box {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: 12px;
  padding: 14px 18px;
  margin: 1.2em 0 1.4em;
  box-shadow: var(--shadow-sm);
  overflow-x: auto;
  max-width: 100%;
}

.blog-post .box .label {
  display: block;
  margin-bottom: 6px;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
}

.blog-post .box.example {
  border-left-color: var(--green);
  background: var(--green-soft);
}

.blog-post .box.example .label {
  color: var(--green);
}

.blog-post .box.warn {
  border-left-color: var(--warn-bar);
  background: var(--method-bg);
}

.blog-post .box.warn .label {
  color: var(--warn);
}

.blog-post .box ul,
.blog-post .box ol {
  margin: 0.4em 0 0;
  padding-left: 1.2em;
}

.blog-post .box li {
  margin: 0.3em 0;
}

.blog-post ol.steps li {
  margin-bottom: 0.55em;
}

.blog-post .blog-table {
  overflow-x: auto;
  max-width: 100%;
  margin: 1.2em 0 1.6em;
}

.blog-post table {
  width: 100%;
  min-width: 720px;
  border-collapse: collapse;
  margin: 0;
  font-size: 0.92rem;
}

.blog-post th,
.blog-post td {
  border: 1px solid var(--border);
  padding: 8px 10px;
  text-align: left;
  vertical-align: top;
}

.blog-post th {
  background: var(--accent-soft);
  color: var(--text);
  font-weight: 800;
}

.blog-post table.matrix {
  width: auto;
  min-width: 0;
  margin: 0.8em auto;
}

.blog-post table.matrix td {
  text-align: center;
  min-width: 2.4em;
}

.blog-post details {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 10px 16px;
  margin: 0.7em 0;
}

.blog-post summary {
  cursor: pointer;
  font-weight: 700;
  color: var(--text);
}

.blog-post details p {
  margin: 0.7em 0 0.3em;
}

.blog-post .box,
.blog-post .blog-table {
  max-width: 100%;
}

.blog-post table.diff th,
.blog-post table.diff td {
  text-align: center;
}

.blog-post figure {
  margin: 1.35em 0 1.55em;
  padding: 16px 12px 12px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  max-width: 100%;
}

.blog-post figure svg {
  width: 100%;
  max-width: 560px;
  height: auto;
  display: block;
  margin: 0 auto;
  overflow: hidden;
  color: var(--text);
}

.blog-post figcaption {
  margin: 10px auto 0;
  max-width: 40rem;
  font-size: 0.9rem;
  line-height: 1.55;
  color: var(--muted);
  text-align: center;
}

.blog-post svg text {
  font-family: Inter, system-ui, sans-serif;
  font-style: italic;
  fill: var(--text);
  stroke: var(--card-bg);
  stroke-width: 0.32em;
  stroke-linejoin: round;
  paint-order: stroke fill;
}

.blog-post svg text.pt {
  font-style: normal;
  font-weight: 700;
}

.blog-post svg text.op,
.blog-post svg text.note {
  font-style: normal;
  font-weight: 500;
}

.blog-post svg text.note {
  fill: var(--muted);
}

.blog-post mjx-container {
  display: inline-block !important;
  max-width: 100% !important;
  min-width: 0 !important;
  overflow-x: auto !important;
  overflow-y: hidden !important;
  vertical-align: middle;
}

.blog-post mjx-container[display="true"] {
  display: block !important;
  margin: 0.6em 0 !important;
}

.blog-next {
  margin-top: 2em;
  color: var(--muted);
}

.site-footer {
  margin-top: 56px;
  padding-top: 22px;
  border-top: 1px solid var(--border);
  text-align: center;
}

.site-footer p {
  margin: 0;
  font-size: 0.85rem;
  color: var(--muted);
}

.site-footer .footer-copy + .footer-links {
  margin-top: 6px;
}

.site-footer a[aria-current="page"] {
  color: var(--text);
}

.site-footer a {
  color: var(--muted);
  font-weight: 600;
}

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

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

@media (min-width: 640px) {
  .topics-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

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

@media (max-width: 600px) {
  .page-shell {
    padding: 20px 14px 48px;
  }

  .chapter-index-grid {
    grid-template-columns: 1fr;
  }

  .statement-card {
    padding: 26px 20px 28px;
  }

  .topic-card-body {
    padding: 16px 16px 16px;
  }

  .topic-card-icon {
    top: 16px;
    right: 16px;
    width: 40px;
    height: 40px;
    border-radius: 10px;
  }

  .topic-hero-icon {
    width: 42px;
    height: 42px;
  }
}

@media print {
  .print-only {
    display: block !important;
  }

  @page {
    margin: 18mm 16mm 18mm;
  }

  html,
  body {
    background: #fff !important;
    color: #111 !important;
    color-scheme: light !important;
    print-color-adjust: exact;
    -webkit-print-color-adjust: exact;
  }

  .page-shell {
    padding: 0;
    max-width: none;
    font-family: Palatino, "Palatino Linotype", "Book Antiqua", Georgia, "Times New Roman", serif;
    font-size: 11pt;
    line-height: 1.45;
    color: #111;
  }

  .brand,
  .brand-hero,
  .topic-hero h1 {
    background: none !important;
    color: #111 !important;
    -webkit-text-fill-color: #111 !important;
  }

  .page-shell:has(.blog-post) .topic-hero {
    display: block !important;
  }

  .top-nav,
  .theme-toggle,
  .crumbs,
  .home-hero,
  .topic-hero,
  .home-how,
  .topic-jump,
  .topic-search,
  .blog-front,
  .chapter-index,
  .chapter-pills,
  .app-select-menu,
  .topic-intro-actions,
  .pagination,
  .test-builder,
  .test-progress,
  .test-results-head,
  .test-toolbar,
  .test-end-actions,
  .test-item-actions,
  .test-results .statement-card-top,
  .statement-card .btn-primary,
  .problem-nav,
  .exam-back-bar,
  .site-footer {
    display: none !important;
  }

  .test-results {
    animation: none;
    display: block !important;
  }

  .test-print-header {
    border-bottom: 3px double #111;
    padding-bottom: 12px;
    margin: 0 0 18px;
    color: #111;
  }

  .test-print-kicker {
    font-size: 9pt;
    letter-spacing: 0.22em;
  }

  .test-print-header h1 {
    font-size: 16pt;
    font-weight: 700;
    color: #111;
    background: none !important;
    -webkit-text-fill-color: #111 !important;
  }

  .test-print-count,
  .test-print-note {
    color: #111;
  }

  .test-print-count {
    font-size: 10.5pt;
  }

  .test-print-note {
    font-size: 10.5pt;
    font-style: italic;
  }

  .test-list {
    display: block;
    counter-reset: exam-q;
  }

  .test-item {
    display: grid;
    grid-template-columns: 2.15em minmax(0, 1fr);
    column-gap: 0.55em;
    counter-increment: exam-q;
    margin: 0;
    padding: 0.7em 0 1.15em;
    break-inside: avoid;
    page-break-inside: avoid;
  }

  .test-item::before {
    content: counter(exam-q) ".";
    font-weight: 700;
    text-align: right;
    line-height: 1.45;
  }

  .statement-card,
  .problem-card,
  .topic-card,
  .test-card {
    break-inside: avoid;
    box-shadow: none !important;
    animation: none;
    background: #fff !important;
    border: none !important;
    border-radius: 0 !important;
  }

  .test-results .statement-card,
  .test-results .test-card {
    position: static;
    overflow: visible;
    padding: 0 !important;
    margin: 0;
    max-width: none;
  }

  .test-results .statement-card::before,
  .test-results .test-card::before {
    display: none !important;
  }

  .test-results .problem-statement,
  .test-results .statement-preview {
    background: transparent !important;
    border: none !important;
    border-radius: 0 !important;
    box-shadow: none !important;
    padding: 0 !important;
    margin: 0 !important;
    color: #111 !important;
    font-size: 11pt;
    line-height: 1.5;
  }

  .test-results .figure-wrap {
    background: transparent !important;
    border: none !important;
    border-radius: 0 !important;
    padding: 0 !important;
    margin: 0.6em 0 !important;
  }

  .test-results .figure-caption {
    color: #111 !important;
  }

  .problem-statement,
  .method-section,
  .remark-section,
  .result-box,
  .figure-wrap {
    background: #fff !important;
    box-shadow: none !important;
  }

  a[href]::after {
    content: none !important;
  }

  mjx-container {
    filter: none !important;
    color: #111 !important;
    -webkit-text-fill-color: #111 !important;
  }
}