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

:root {
  --color-bg: #f4f6f8;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-muted: #4b5563;
  --color-primary: #1d4ed8;
  --color-primary-hover: #1e40af;
  --color-secondary: #e5e7eb;
  --color-secondary-hover: #d1d5db;
  --color-secondary-text: #1f2937;
  --color-border: #d1d5db;
  --color-error: #b91c1c;
  --color-result-bg: #eff6ff;
  --color-diagram-rise: #2563eb;
  --color-diagram-run: #059669;
  --color-diagram-rafter: #7c3aed;
  --radius: 12px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
  --focus-ring: 0 0 0 3px rgba(29, 78, 216, 0.25);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  padding: 0.75rem 1rem;
  background: var(--color-primary);
  color: #ffffff;
  text-decoration: none;
  border-radius: 0 0 8px 0;
}

.skip-link:focus {
  left: 0;
  outline: none;
  box-shadow: var(--focus-ring);
}

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

.page {
  width: 100%;
  max-width: 920px;
  margin: 0 auto;
  padding: 2rem 1.5rem 3rem;
}

.header {
  text-align: center;
  margin-bottom: 2rem;
}

.header h1 {
  font-size: clamp(1.5rem, 4vw, 2rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.subtitle {
  margin-top: 0.75rem;
  color: var(--color-text-muted);
  font-size: 1rem;
  max-width: 36rem;
  margin-left: auto;
  margin-right: auto;
}

.calculator {
  background: var(--color-surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.75rem;
  margin-bottom: 2.5rem;
}

.calculator-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  align-items: start;
}

.form {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.input-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.input-group label {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text);
}

.input-help {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.input-group input,
.input-group select {
  padding: 0.75rem 1rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-size: 1rem;
  color: var(--color-text);
  background: #ffffff;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.input-group input:focus,
.input-group select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--focus-ring);
}

.input-group input:focus-visible,
.input-group select:focus-visible {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: var(--focus-ring);
}

.input-group select {
  width: 100%;
  cursor: pointer;
}

.measurement-input {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 0.65rem;
}

.measurement-input input {
  width: 100%;
  min-width: 0;
}

.unit-suffix {
  min-width: 2rem;
  color: var(--color-text-muted);
  font-weight: 600;
}

.input-group input[aria-invalid="true"] {
  border-color: var(--color-error);
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 0.25rem;
}

.btn {
  padding: 0.85rem 1.5rem;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  border: 2px solid transparent;
  transition: background-color 0.2s, border-color 0.2s, transform 0.1s;
}

.btn:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  background-color: var(--color-primary);
  color: #ffffff;
}

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

.btn-secondary {
  background-color: var(--color-secondary);
  color: var(--color-secondary-text);
}

.btn-secondary:hover {
  background-color: var(--color-secondary-hover);
}

.error-message {
  margin-top: 1rem;
  color: var(--color-error);
  font-size: 0.875rem;
  font-weight: 600;
}

.results {
  margin-top: 2rem;
  padding-top: 2rem;
  border-top: 1px solid var(--color-border);
}

.results-heading {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 1rem;
}

.results-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.result-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.25rem;
  background: var(--color-result-bg);
  border-radius: 8px;
}

.result-item dt {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-muted);
}

.result-item dd {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  text-align: right;
}

.result-item-measurements {
  align-items: flex-start;
}

.result-item-measurements dd {
  max-width: 60%;
  font-size: 1rem;
}

.result-classification {
  margin-top: 1.25rem;
  font-size: 0.95rem;
}

.result-classification-label {
  color: var(--color-text-muted);
  margin-right: 0.35rem;
}

.classification-guide {
  margin-top: 0.75rem;
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.classification-guide summary {
  width: fit-content;
  color: var(--color-primary);
  font-weight: 600;
  cursor: pointer;
}

.classification-guide summary:focus-visible {
  outline: none;
  border-radius: 3px;
  box-shadow: var(--focus-ring);
}

.classification-guide dl {
  margin-top: 0.65rem;
}

.classification-guide dl div {
  display: grid;
  grid-template-columns: minmax(7.5rem, auto) 1fr;
  gap: 0.75rem;
  padding: 0.25rem 0;
}

.classification-guide dt {
  font-weight: 700;
  color: var(--color-text);
}

.disclaimer {
  margin-top: 0.5rem;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
}

.result-explanation {
  margin-top: 0.75rem;
  font-size: 0.95rem;
  color: var(--color-text);
}

.diagram-panel {
  background: #f8fafc;
  border: 1px solid var(--color-border);
  border-radius: 10px;
  padding: 1rem;
  min-height: 220px;
}

.diagram-heading {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: 0.75rem;
  text-align: center;
}

.roof-diagram {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 180px;
}

.diagram-placeholder {
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.9rem;
  padding: 1rem;
}

.roof-svg {
  width: 100%;
  max-width: 100%;
  height: 220px;
  display: block;
}

.diagram-rise {
  stroke: var(--color-diagram-rise);
  stroke-width: 3;
}

.diagram-run {
  stroke: var(--color-diagram-run);
  stroke-width: 3;
}

.diagram-rafter {
  stroke: var(--color-diagram-rafter);
  stroke-width: 3;
}

.diagram-label {
  font-size: 18px;
  font-weight: 600;
  fill: var(--color-text);
}

.content-section {
  background: var(--color-surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.75rem;
  margin-bottom: 1.5rem;
}

.content-section h2 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}

.content-section p {
  color: var(--color-text-muted);
}

.content-list {
  margin-left: 1.25rem;
  color: var(--color-text-muted);
}

.content-list li + li {
  margin-top: 0.5rem;
}

.table-wrapper {
  overflow-x: auto;
  margin-top: 1rem;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9375rem;
}

.data-table th,
.data-table td {
  padding: 0.75rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}

.data-table th {
  background: var(--color-result-bg);
  font-weight: 700;
  color: var(--color-text);
}

.data-table tbody tr:hover {
  background: #f9fafb;
}

.faq-list {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.faq-item dt {
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 0.35rem;
}

.faq-item dd {
  color: var(--color-text-muted);
}

.related-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.related-list li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.85rem 1rem;
  background: var(--color-result-bg);
  border-radius: 8px;
}

.related-name {
  font-weight: 600;
  color: var(--color-text);
}

.badge {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  background: var(--color-secondary);
  padding: 0.25rem 0.6rem;
  border-radius: 999px;
}

.site-footer {
  max-width: 920px;
  margin: 0 auto;
  padding: 0 1.5rem 2rem;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.8125rem;
}

.site-footer p + p {
  margin-top: 0.35rem;
}

@media (max-width: 768px) {
  .calculator-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .page {
    padding: 1.25rem 1rem 2rem;
  }

  .calculator,
  .content-section {
    padding: 1.25rem;
  }

  .button-row {
    flex-direction: column;
  }

  .button-row .btn {
    width: 100%;
  }

  .result-item dd {
    font-size: 1.1rem;
  }

  .result-item-measurements {
    flex-direction: column;
    align-items: flex-start;
  }

  .result-item-measurements dd {
    max-width: none;
    text-align: left;
    font-size: 0.95rem;
  }

  .classification-guide dl div {
    grid-template-columns: 1fr;
    gap: 0;
  }

  .related-list li {
    flex-direction: column;
    align-items: flex-start;
  }

  .site-footer {
    padding: 0 1rem 1.5rem;
  }
}