:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-secondary: #16a34a;
  --color-accent: #ea580c;
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-text: #1e293b;
  --color-text-light: #64748b;
  --color-border: #e2e8f0;
  --color-success: #16a34a;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
  --radius: 8px;
  --max-width: 1200px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
}

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

a:hover {
  color: var(--color-primary-dark);
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1rem;
}

.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  background: var(--color-primary);
  color: white;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.2s;
}

.btn:hover {
  background: var(--color-primary-dark);
  color: white;
}

.card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

header {
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  padding: 1rem 0;
}

header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

header .logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
}

header nav a {
  margin-left: 1.5rem;
  color: var(--color-text-light);
}

header nav a:hover {
  color: var(--color-primary);
}

footer {
  background: var(--color-bg-alt);
  border-top: 1px solid var(--color-border);
  padding: 2rem 0;
  margin-top: 3rem;
  text-align: center;
  color: var(--color-text-light);
}

.hero {
  text-align: center;
  padding: 3rem 1rem;
  background: var(--color-bg-alt);
}

.hero h1 {
  font-size: 2rem;
  margin-bottom: 1rem;
  color: var(--color-text);
}

.hero p {
  font-size: 1.125rem;
  color: var(--color-text-light);
  max-width: 600px;
  margin: 0 auto;
}

.calculator-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
  padding: 2rem 0;
}

.calculator-card {
  display: block;
  padding: 1.25rem;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  color: var(--color-text);
  transition: box-shadow 0.2s, border-color 0.2s;
}

.calculator-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary);
}

.calculator-card h3 {
  font-size: 1rem;
  margin-bottom: 0.25rem;
}

.calculator-card p {
  font-size: 0.875rem;
  color: var(--color-text-light);
}

.calculator-form {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin: 1.5rem 0;
}

.calculator-form h2 {
  margin-bottom: 1rem;
  font-size: 1.25rem;
}

.form-group {
  margin-bottom: 1rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.25rem;
  font-weight: 500;
  color: var(--color-text);
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 1rem;
  background: var(--color-bg);
  color: var(--color-text);
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.1);
}

.form-group[hidden] {
  display: none !important;
}

.field-hint {
  margin-top: 0.4rem;
  color: var(--color-text-light);
  font-size: 0.875rem;
}

.result-box {
  background: var(--color-bg-alt);
  border: 2px solid var(--color-secondary);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin: 1.5rem 0;
  text-align: center;
}

.result-box.is-error {
  border-color: #dc2626;
}

.result-box .score {
  font-size: 3rem;
  font-weight: 700;
  color: var(--color-secondary);
}

.result-box .label {
  color: var(--color-text-light);
  margin-top: 0.5rem;
}

.result-hint {
  margin-top: 0.5rem;
  color: var(--color-text-light);
  font-size: 0.875rem;
}

.result-details {
  margin-top: 1rem;
}

.result-detail-list {
  list-style: none;
  display: grid;
  gap: 0.5rem;
  text-align: left;
}

.result-detail-list li {
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  color: var(--color-text-light);
}

.faq-section {
  margin: 2rem 0;
}

.faq-section h2 {
  margin-bottom: 1rem;
}

.faq-item {
  border-bottom: 1px solid var(--color-border);
  padding: 1rem 0;
}

.faq-item:last-child {
  border-bottom: none;
}

.faq-item h3 {
  font-size: 1rem;
  margin-bottom: 0.5rem;
}

.faq-item p {
  color: var(--color-text-light);
  font-size: 0.95rem;
}

.related-links {
  margin: 2rem 0;
}

.related-links h2 {
  font-size: 1.25rem;
  margin-bottom: 1rem;
}

.related-links ul {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 0.5rem;
}

.related-links li a {
  display: block;
  padding: 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
}

.related-links li a:hover {
  border-color: var(--color-primary);
  background: var(--color-bg-alt);
}

.section {
  padding: 2rem 0;
}

.section-alt {
  background: var(--color-bg-alt);
}

.content-section {
  max-width: 720px;
  margin: 0 auto;
}

.content-section h2 {
  margin: 1.5rem 0 0.75rem;
}

.content-section p {
  margin-bottom: 1rem;
  color: var(--color-text-light);
}

.page-intro-stack {
  margin-bottom: 1rem;
}

.page-intro-stack .page-intro {
  margin: 1rem 0;
}

.content-card-section {
  margin-top: 2rem;
}

.content-example-card {
  padding: 1rem 1.25rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg-alt);
}

.content-example-card h3 {
  margin-bottom: 0.75rem;
}

.content-step-list {
  margin: 0.5rem 0 0;
  padding-left: 1.25rem;
  display: grid;
  gap: 0.75rem;
  color: var(--color-text-light);
}

.content-step-list li {
  padding-left: 0.2rem;
}

.formula-chip {
  display: inline-flex;
  align-items: center;
  margin: 0.75rem 0 1.25rem;
  padding: 0.65rem 0.85rem;
  border-radius: 999px;
  background: rgba(37, 99, 235, 0.08);
  color: var(--color-primary-dark);
  font-weight: 600;
}

@media (max-width: 768px) {
  .hero h1 {
    font-size: 1.5rem;
  }

  .calculator-grid {
    grid-template-columns: 1fr;
  }

  header .container {
    flex-direction: column;
    gap: 0.75rem;
  }

  header nav a {
    margin-left: 0;
    margin-right: 1rem;
  }
}

.error-404-code {
  font-size: 6rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: 0.5rem;
}

.error-404-subtitle {
  font-size: 1.25rem;
  color: var(--color-text-light);
  margin-bottom: 1.5rem;
}

.search-404 {
  max-width: 500px;
  margin: 1.5rem auto;
}

.search-404 input {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 2px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 1rem;
  transition: border-color 0.2s;
}

.search-404 input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-results {
  margin-top: 1rem;
  text-align: left;
}

.search-results a {
  display: block;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  margin-bottom: 0.5rem;
  color: var(--color-text);
}

.search-results a:hover {
  border-color: var(--color-primary);
  background: var(--color-bg-alt);
}

.quick-links {
  margin-top: 2rem;
  text-align: center;
}

.quick-links h3 {
  margin-bottom: 1rem;
  color: var(--color-text-light);
  font-size: 1rem;
}

.quick-links-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 0.75rem;
  max-width: 600px;
  margin: 0 auto;
}

.quick-links-grid a {
  display: block;
  padding: 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 0.875rem;
  color: var(--color-text);
}

.quick-links-grid a:hover {
  border-color: var(--color-primary);
  background: var(--color-bg-alt);
}

footer nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.25rem;
}

footer nav a {
  color: var(--color-text-light);
  font-size: 0.875rem;
}

footer nav a:hover {
  color: var(--color-primary);
}

.content-section h3 {
  margin: 1.25rem 0 0.5rem;
  font-size: 1.1rem;
}

.content-section ul {
  margin: 0.75rem 0 1rem 1.5rem;
  color: var(--color-text-light);
}

.content-section ul li {
  margin-bottom: 0.25rem;
}

textarea {
  font-family: inherit;
  resize: vertical;
}

main {
  display: block;
}

.hero-home {
  padding: 4rem 0;
  text-align: left;
  background:
    linear-gradient(180deg, rgba(37, 99, 235, 0.06) 0%, rgba(255, 255, 255, 0) 100%),
    var(--color-bg-alt);
}

.hero-home-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(280px, 0.85fr);
  gap: 2rem;
  align-items: start;
}

.hero-home h1 {
  font-size: clamp(2.5rem, 5vw, 4rem);
  line-height: 1.05;
  text-align: left;
  margin-bottom: 1rem;
}

.eyebrow {
  display: inline-block;
  margin-bottom: 0.75rem;
  color: var(--color-accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.hero-lead {
  max-width: 44rem;
  margin: 0 0 1.25rem;
  color: var(--color-text-light);
  font-size: 1.1rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.btn-secondary {
  background: transparent;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover {
  background: var(--color-bg-alt);
  color: var(--color-text);
  border-color: var(--color-primary);
}

.hero-panel {
  padding: 1.5rem;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.hero-panel h2 {
  margin-bottom: 1rem;
  font-size: 1.2rem;
}

.hero-panel ul {
  list-style: none;
}

.hero-panel li + li {
  border-top: 1px solid var(--color-border);
}

.hero-panel a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.85rem 0;
  color: var(--color-text);
  font-weight: 600;
}

.hero-panel a:hover {
  color: var(--color-primary);
}

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

.metric-card {
  display: grid;
  gap: 0.35rem;
  padding: 1.25rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  text-align: center;
  box-shadow: var(--shadow-sm);
}

.metric-card strong {
  font-size: 2rem;
  line-height: 1;
  color: var(--color-text);
}

.metric-card span {
  color: var(--color-text-light);
}

.task-group-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
}

.task-group {
  padding: 1.25rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  box-shadow: var(--shadow-sm);
}

.task-group h3 {
  margin-bottom: 0.5rem;
}

.task-group p {
  margin-bottom: 1rem;
  color: var(--color-text-light);
}

.task-group-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.task-group-links a {
  display: inline-flex;
  align-items: center;
  padding: 0.45rem 0.7rem;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  color: var(--color-text);
  background: var(--color-bg-alt);
}

.task-group-links a:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.section-heading {
  max-width: 720px;
  margin: 0 auto 1.5rem;
  text-align: center;
}

.section-heading h2 {
  margin-bottom: 0.75rem;
}

.section-heading p {
  color: var(--color-text-light);
}

.subject-group-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}

.subject-group {
  padding: 1.25rem;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.subject-group h3 {
  margin-bottom: 0.5rem;
}

.subject-group p {
  margin-bottom: 1rem;
  color: var(--color-text-light);
  font-size: 0.95rem;
}

.subject-group ul {
  list-style: none;
  display: grid;
  gap: 0.55rem;
}

.subject-group a {
  color: var(--color-text);
}

.subject-group a:hover {
  color: var(--color-primary);
}

.page-shell {
  padding: 2rem 1rem;
}

.page-content {
  max-width: 720px;
  margin: 0 auto;
}

.page-intro {
  color: var(--color-text-light);
  margin: 1rem 0;
}

.calculator-subnav {
  margin: 0 0 1.5rem;
  padding: 0.85rem 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg-alt);
}

.calculator-subnav p {
  margin: 0;
  color: var(--color-text-light);
}

.calculator-subnav strong {
  color: var(--color-text);
}

.inline-link-list {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.inline-link-list a {
  display: inline-flex;
  align-items: center;
  padding: 0.4rem 0.65rem;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: var(--color-bg);
  color: var(--color-text);
}

.inline-link-list a:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.breadcrumbs {
  margin-bottom: 0.75rem;
}

.breadcrumbs ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  color: var(--color-text-light);
  font-size: 0.9rem;
}

.breadcrumbs li {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.breadcrumbs li + li::before {
  content: "/";
  color: var(--color-border);
}

.breadcrumbs a {
  color: var(--color-text-light);
}

.breadcrumbs a:hover {
  color: var(--color-primary);
}

.last-updated {
  margin-bottom: 1.25rem;
  color: var(--color-text-light);
  font-size: 0.9rem;
}

.last-updated span {
  margin-right: 0.35rem;
  color: var(--color-text);
  font-weight: 600;
}

.related-links p {
  max-width: 48rem;
  margin-bottom: 1rem;
  color: var(--color-text-light);
}

.home-guidance {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
  margin-top: 2rem;
}

.home-guidance-block {
  padding: 1.25rem;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
}

.home-guidance-block h3 {
  margin-bottom: 0.5rem;
  font-size: 1rem;
}

.home-guidance-block p {
  color: var(--color-text-light);
}

@media (max-width: 768px) {
  .hero-home {
    padding: 3rem 0;
  }

  .hero-home-grid {
    grid-template-columns: 1fr;
  }

  .site-metrics {
    grid-template-columns: 1fr;
  }

  .hero-actions {
    flex-direction: column;
    align-items: flex-start;
  }

  .hero-actions .btn {
    width: 100%;
    text-align: center;
  }
}

footer nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.25rem;
}

footer nav a {
  color: var(--color-text-light);
  font-size: 0.875rem;
}

footer nav a:hover {
  color: var(--color-primary);
}

.content-section h3 {
  margin: 1.25rem 0 0.5rem;
  font-size: 1.1rem;
}

.content-section ul {
  margin: 0.75rem 0 1rem 1.5rem;
  color: var(--color-text-light);
}

.content-section ul li {
  margin-bottom: 0.25rem;
}

textarea {
  font-family: inherit;
  resize: vertical;
}