/* ==========================================================================
   GravelDrivewayCalc - Global Stylesheet (style.css)
   Mobile-first, fully responsive, zero external dependencies.
   ========================================================================== */

:root {
  /* Brand Colors */
  --color-primary: #1b4332;
  --color-primary-hover: #143527;
  --color-primary-light: #2d6a4f;
  --color-primary-subtle: #eef7f2;
  --color-accent: #40916c;
  --color-accent-soft: #d8f3dc;

  /* Neutrals */
  --color-bg: #f8faf8;
  --color-surface: #ffffff;
  --color-surface-alt: #f1f5f2;
  --color-border: #dbe4dd;
  --color-border-light: #e8eee9;

  /* Text Colors */
  --color-text-main: #19221d;
  --color-text-secondary: #4a5950;
  --color-text-muted: #6e7e74;
  --color-text-inverse: #ffffff;

  /* Status Colors */
  --color-error: #c53030;
  --color-error-bg: #fff5f5;
  --color-error-border: #feb2b2;
  --color-success: #276749;
  --color-success-bg: #f0fff4;

  /* Typography */
  --font-family-base: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-family-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  /* Elevations & Radii */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.04);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-full: 9999px;

  /* Sizing */
  --container-max: 1140px;
  --content-max: 820px;
  --header-height: 72px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family-base);
  background-color: var(--color-bg);
  color: var(--color-text-main);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

:focus-visible {
  outline: 3px solid var(--color-primary-light);
  outline-offset: 2px;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  background: var(--color-primary);
  color: #fff;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  z-index: 9999;
  font-weight: 600;
  text-decoration: none;
  transition: top 0.2s ease;
}

.skip-link:focus {
  top: 1rem;
}

/* Layout Containers */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-left: auto;
  margin-right: auto;
  padding-left: 1.25rem;
  padding-right: 1.25rem;
}

.container-narrow {
  max-width: var(--content-max);
}

/* Header & Navigation */
.site-header {
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-height);
  display: flex;
  align-items: center;
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.logo-group {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  text-decoration: none;
  color: var(--color-primary);
  font-weight: 800;
  font-size: 1.25rem;
  letter-spacing: -0.02em;
}

.logo-icon {
  width: 34px;
  height: 34px;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
  color: white;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 4px rgba(27, 67, 50, 0.25);
}

.logo-text span {
  color: var(--color-accent);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 0.85rem;
  align-items: center;
}

.nav-link {
  color: var(--color-text-secondary);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.925rem;
  padding: 0.4rem 0.75rem;
  border-radius: var(--radius-sm);
  transition: color 0.15s ease, background-color 0.15s ease;
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-primary);
  background-color: var(--color-primary-subtle);
}

.nav-cta {
  background-color: var(--color-primary);
  color: #fff !important;
  font-weight: 600;
  padding: 0.5rem 1.1rem;
  border-radius: var(--radius-sm);
}

.nav-cta:hover {
  background-color: var(--color-primary-hover) !important;
}

.mobile-nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 0.5rem;
  cursor: pointer;
  color: var(--color-text-main);
}

@media (max-width: 860px) {
  .mobile-nav-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .main-nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: 1.25rem;
    box-shadow: var(--shadow-md);
    transform: translateY(-160%);
    transition: transform 0.25s ease-in-out;
  }

  .main-nav.nav-open {
    transform: translateY(0);
  }

  .nav-links {
    flex-direction: column;
    width: 100%;
    align-items: stretch;
    gap: 0.5rem;
  }

  .nav-link {
    padding: 0.75rem 1rem;
    display: block;
    text-align: center;
  }
}

/* Breadcrumbs */
.breadcrumbs-bar {
  padding: 0.85rem 0;
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border-light);
  font-size: 0.85rem;
}

.breadcrumbs-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.4rem;
  list-style: none;
  color: var(--color-text-muted);
}

.breadcrumbs-list a {
  color: var(--color-primary-light);
  text-decoration: none;
}

.breadcrumbs-list a:hover {
  text-decoration: underline;
}

.breadcrumbs-separator {
  color: var(--color-border);
  font-size: 0.8rem;
}

/* Hero Section */
.hero-section {
  padding: 2.75rem 0 1.75rem 0;
  text-align: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background-color: var(--color-accent-soft);
  color: var(--color-primary);
  font-size: 0.825rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.3rem 0.75rem;
  border-radius: var(--radius-full);
  margin-bottom: 1rem;
}

.hero-title {
  font-size: 2.35rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1.2;
  letter-spacing: -0.025em;
  margin-bottom: 0.85rem;
}

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--color-text-secondary);
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.55;
}

/* Calculator Component */
.calculator-section {
  padding-bottom: 3.5rem;
}

.calculator-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}

.calc-header-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.75rem;
  background-color: var(--color-surface-alt);
  border-bottom: 1px solid var(--color-border);
  gap: 1rem;
}

.calc-header-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.unit-switch-group {
  display: inline-flex;
  background: #e2e8e3;
  padding: 3px;
  border-radius: var(--radius-full);
  border: 1px solid var(--color-border);
}

.unit-switch-btn {
  border: none;
  background: transparent;
  padding: 0.45rem 1.15rem;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all 0.2s ease;
}

.unit-switch-btn.active {
  background-color: var(--color-primary);
  color: #fff;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.12);
}

.calc-body {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  padding: 1.75rem;
}

@media (min-width: 860px) {
  .calc-body {
    grid-template-columns: 1.15fr 0.95fr;
    gap: 2.25rem;
  }
}

.calc-inputs-pane {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 480px) {
  .form-row-2col {
    grid-template-columns: 1fr 1fr;
  }
  .form-row-3col {
    grid-template-columns: repeat(3, 1fr);
  }
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.form-label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-main);
}

.form-label-hint {
  font-weight: 400;
  color: var(--color-text-muted);
  font-size: 0.8rem;
}

.input-with-unit {
  position: relative;
  display: flex;
  align-items: center;
}

.form-input,
.form-select,
.form-textarea {
  width: 100%;
  padding: 0.75rem 0.85rem;
  font-size: 1.05rem;
  font-family: inherit;
  color: var(--color-text-main);
  background-color: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.form-input {
  padding-right: 3.5rem;
}

.form-input:hover,
.form-select:hover,
.form-textarea:hover {
  border-color: #b5c4b8;
}

.form-input:focus,
.form-select:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(27, 67, 50, 0.15);
}

.form-input.is-invalid {
  border-color: var(--color-error);
  background-color: var(--color-error-bg);
}

.input-unit-badge {
  position: absolute;
  right: 0.75rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-text-muted);
  pointer-events: none;
  background: var(--color-surface-alt);
  padding: 0.2rem 0.45rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-border-light);
}

.form-helper {
  font-size: 0.785rem;
  color: var(--color-text-muted);
  margin-top: 0.1rem;
}

.field-error-msg {
  display: none;
  font-size: 0.785rem;
  color: var(--color-error);
  font-weight: 500;
  margin-top: 0.2rem;
}

.field-error-msg.visible {
  display: block;
}

.quick-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.35rem;
}

.pill-btn {
  background: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 0.25rem 0.6rem;
  font-size: 0.775rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all 0.15s ease;
}

.pill-btn:hover {
  background: #e2ede5;
  color: var(--color-primary);
  border-color: var(--color-accent);
}

.pill-btn.active {
  background: var(--color-primary-subtle);
  color: var(--color-primary);
  border-color: var(--color-primary);
  box-shadow: 0 1px 2px rgba(27, 67, 50, 0.1);
}

.select-wrapper {
  position: relative;
}

.form-select {
  padding-right: 2.2rem;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' fill='%234a5950' viewBox='0 0 16 16'%3E%3Cpath fill-rule='evenodd' d='M1.646 4.646a.5.5 0 0 1 .708 0L8 10.293l5.646-5.647a.5.5 0 0 1 .708.708l-6 6a.5.5 0 0 1-.708 0l-6-6a.5.5 0 0 1 0-.708z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.85rem center;
  cursor: pointer;
}

/* Results Pane */
.calc-results-pane {
  background-color: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.35rem;
  position: sticky;
  top: calc(var(--header-height) + 1.25rem);
}

.results-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 0.85rem;
}

.results-heading {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-primary);
}

.live-indicator {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--color-primary-light);
  letter-spacing: 0.05em;
}

.live-dot {
  width: 8px;
  height: 8px;
  background-color: var(--color-accent);
  border-radius: 50%;
  animation: pulse-dot 2s infinite ease-in-out;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.4; transform: scale(0.85); }
}

.results-primary-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.85rem;
}

.highlight-card {
  background: #ffffff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.15rem 1rem;
  text-align: center;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.highlight-card.recommended {
  border: 2px solid var(--color-primary);
  background: linear-gradient(180deg, #ffffff 0%, var(--color-primary-subtle) 100%);
}

.highlight-title {
  font-size: 0.775rem;
  text-transform: uppercase;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--color-text-secondary);
  margin-bottom: 0.35rem;
}

.highlight-val {
  font-size: 1.95rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1.1;
  font-feature-settings: "tnum";
}

.highlight-unit {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-top: 0.25rem;
}

.results-breakdown-list {
  background-color: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.breakdown-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--color-border-light);
  font-size: 0.9rem;
}

.breakdown-row:last-child {
  border-bottom: none;
}

.breakdown-label {
  color: var(--color-text-secondary);
  font-weight: 500;
}

.breakdown-val {
  font-weight: 700;
  color: var(--color-text-main);
  font-family: var(--font-family-mono);
  font-size: 0.95rem;
}

.calc-actions {
  display: flex;
  gap: 0.75rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.15s ease;
  border: 1px solid transparent;
  text-decoration: none;
}

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

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

.btn-primary.copied {
  background-color: #1b4332;
  color: #fff;
  border-color: #1b4332;
}

.btn-outline {
  background-color: #fff;
  border-color: var(--color-border);
  color: var(--color-text-secondary);
}

.btn-outline:hover {
  background-color: var(--color-surface-alt);
  color: var(--color-text-main);
  border-color: #bdcbbd;
}

.toast-notice {
  display: none;
  align-items: center;
  gap: 0.5rem;
  background-color: var(--color-primary);
  color: #fff;
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.6rem 1rem;
  border-radius: var(--radius-sm);
  text-align: center;
  justify-content: center;
  animation: fadeInToast 0.25s ease forwards;
}

.toast-notice.visible {
  display: flex;
}

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

.calc-disclaimer {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  line-height: 1.45;
  background-color: rgba(255, 255, 255, 0.75);
  padding: 0.75rem;
  border-radius: var(--radius-sm);
  border-left: 3px solid var(--color-accent);
}

/* Editorial & Guide Content */
.content-section {
  padding: 3.5rem 0;
  border-top: 1px solid var(--color-border);
}

.content-section.alt-bg {
  background-color: #ffffff;
}

.section-header {
  margin-bottom: 2rem;
  max-width: 820px;
}

.section-tag {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--color-primary-light);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 0.35rem;
}

.section-title {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1.25;
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
}

.section-description {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

.guide-article {
  max-width: 820px;
  margin-left: auto;
  margin-right: auto;
}

.guide-article h2 {
  font-size: 1.55rem;
  font-weight: 800;
  color: var(--color-primary);
  margin-top: 2.25rem;
  margin-bottom: 0.85rem;
  line-height: 1.3;
}

.guide-article h3 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text-main);
  margin-top: 1.5rem;
  margin-bottom: 0.65rem;
}

.guide-article p {
  font-size: 1rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: 1.25rem;
}

.guide-article ul,
.guide-article ol {
  margin-bottom: 1.25rem;
  padding-left: 1.5rem;
  color: var(--color-text-secondary);
  line-height: 1.65;
}

.guide-article li {
  margin-bottom: 0.5rem;
}

/* Callouts & Alert Boxes */
.callout-box {
  background-color: var(--color-surface-alt);
  border-left: 4px solid var(--color-primary);
  padding: 1.25rem;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin: 1.5rem 0;
}

.callout-title {
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 0.35rem;
}

.callout-box p:last-child {
  margin-bottom: 0;
}

/* Formula Callouts */
.formula-code-box {
  background-color: var(--color-surface-alt);
  border-left: 4px solid var(--color-primary-light);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 1rem 1.25rem;
  font-family: var(--font-family-mono);
  font-size: 0.885rem;
  color: var(--color-text-main);
  line-height: 1.7;
  margin: 1.25rem 0;
}

/* Data Tables */
.data-table-container {
  overflow-x: auto;
  margin: 1.75rem 0;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  -webkit-overflow-scrolling: touch;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.925rem;
}

.data-table th,
.data-table td {
  padding: 0.85rem 1.15rem;
  border-bottom: 1px solid var(--color-border-light);
}

.data-table th {
  background-color: var(--color-surface-alt);
  font-weight: 700;
  color: var(--color-primary);
  white-space: nowrap;
}

.data-table tr:last-child td {
  border-bottom: none;
}

.data-table tbody tr:hover {
  background-color: var(--color-primary-subtle);
}

.table-calc-btn {
  background-color: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  color: var(--color-primary);
  font-weight: 600;
  font-size: 0.8rem;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.15s ease;
}

.table-calc-btn:hover {
  background-color: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.table-badge {
  display: inline-block;
  font-size: 0.775rem;
  font-weight: 600;
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  background: #e9ecef;
  color: #495057;
}

.table-badge.recommended-badge {
  background: var(--color-accent-soft);
  color: var(--color-primary);
}

/* Depth Cards Grid */
.depth-cards-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
  margin: 1.5rem 0;
}

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

@media (min-width: 1024px) {
  .depth-cards-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.depth-card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  border-top: 4px solid var(--color-primary-light);
  box-shadow: var(--shadow-sm);
}

.depth-badge {
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--color-primary);
  margin-bottom: 0.35rem;
}

.depth-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text-main);
  margin-bottom: 0.5rem;
}

.depth-text {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
}

/* Related Cards Grid */
.related-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
  margin-top: 1.5rem;
}

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

@media (min-width: 1024px) {
  .related-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.related-card {
  background: #ffffff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.related-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-accent);
}

.related-card-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 0.45rem;
}

.related-card-desc {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
  margin-bottom: 0.75rem;
}

.related-card-link {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-accent);
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

/* FAQ Accordion */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  max-width: 860px;
}

.faq-item {
  background: #ffffff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.faq-question {
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  padding: 1.25rem 1.5rem;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text-main);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  transition: background-color 0.15s ease;
}

.faq-question:hover {
  background-color: var(--color-surface-alt);
  color: var(--color-primary);
}

.faq-icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
  color: var(--color-primary);
  transition: transform 0.2s ease;
}

.faq-item.open .faq-icon {
  transform: rotate(180deg);
}

.faq-answer {
  display: none;
  padding: 0 1.5rem 1.25rem 1.5rem;
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  line-height: 1.65;
  border-top: 1px solid var(--color-border-light);
  padding-top: 1rem;
}

.faq-item.open .faq-answer {
  display: block;
}

/* Non-intrusive Ad Placeholder (Zero scripts, subtle design) */
.ad-slot-placeholder {
  background-color: var(--color-surface-alt);
  border: 1px dashed var(--color-border);
  border-radius: var(--radius-md);
  padding: 1rem;
  margin: 2.5rem 0;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.775rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

/* Institutional & Contact Pages */
.legal-card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 2.5rem 2rem;
  box-shadow: var(--shadow-sm);
  margin-bottom: 3rem;
}

.legal-card h2 {
  font-size: 1.35rem;
  color: var(--color-primary);
  margin-top: 2rem;
  margin-bottom: 0.75rem;
}

.legal-card p {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
  margin-bottom: 1rem;
}

.legal-card ul {
  padding-left: 1.5rem;
  margin-bottom: 1.25rem;
  color: var(--color-text-secondary);
  font-size: 0.95rem;
}

.legal-card li {
  margin-bottom: 0.45rem;
}

.config-alert {
  background-color: #fff9db;
  border: 1px solid #ffe066;
  border-left: 4px solid #f59f00;
  padding: 1rem;
  border-radius: var(--radius-sm);
  margin: 1.5rem 0;
  font-size: 0.9rem;
  color: #664d03;
}

/* Contact Form */
.contact-form {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  margin-top: 1.5rem;
}

.form-textarea {
  resize: vertical;
  min-height: 130px;
}

/* 404 Error Page */
.error-hero {
  padding: 4.5rem 0;
  text-align: center;
}

.error-code {
  font-size: 5rem;
  font-weight: 900;
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: 0.75rem;
}

.error-title {
  font-size: 1.85rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.error-desc {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  max-width: 500px;
  margin: 0 auto 2rem auto;
}

.error-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
}

/* Footer */
.site-footer {
  background-color: var(--color-primary);
  color: #ffffff;
  padding: 3.5rem 0 2rem 0;
  margin-top: auto;
}

.footer-top {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2.5rem;
  margin-bottom: 2.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.12);
  padding-bottom: 2.5rem;
}

@media (min-width: 768px) {
  .footer-top {
    grid-template-columns: 2fr 1fr 1fr 1fr;
  }
}

.footer-brand .logo-group {
  color: #fff;
  margin-bottom: 1rem;
}

.footer-brand p {
  color: rgba(255, 255, 255, 0.75);
  font-size: 0.9rem;
  line-height: 1.6;
  max-width: 340px;
}

.footer-col-title {
  font-size: 0.95rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: #fff;
  margin-bottom: 1rem;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.footer-link {
  color: rgba(255, 255, 255, 0.75);
  text-decoration: none;
  font-size: 0.885rem;
  transition: color 0.15s ease;
}

.footer-link:hover {
  color: #fff;
}

.footer-bottom {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  font-size: 0.825rem;
  color: rgba(255, 255, 255, 0.6);
  justify-content: space-between;
}

@media (min-width: 640px) {
  .footer-bottom {
    flex-direction: row;
    align-items: center;
  }
}

/* Print Styles */
@media print {
  body { background: #fff; color: #000; }
  .site-header, .mobile-nav-toggle, .calc-actions, .unit-switch-group,
  .quick-pills, .site-footer, .skip-link, .table-calc-btn, .ad-slot-placeholder {
    display: none !important;
  }
  .calculator-card { border: 1px solid #000; box-shadow: none; page-break-inside: avoid; }
  .calc-body { display: block; }
  .calc-results-pane { position: static; border: 1px solid #999; margin-top: 1rem; background: none; }
}

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

/* Calculator Planning Assumption Banner */
.calc-assumption-banner {
  background-color: var(--color-surface-alt);
  border-bottom: 1px solid var(--color-border);
  padding: 0.85rem 1.5rem;
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
}
.calc-assumption-banner strong {
  color: var(--color-primary-dark);
}


/* Batch 1 fixes (2026-10-03) */
/* Keep each formula on its own line; the HTML relies on line breaks */
.formula-code-box {
  white-space: pre-line;
  padding-top: 0;
}

/* Hide empty ad placeholders until an ad network is actually live */
.ad-slot-placeholder {
  display: none;
}


/* EEAT / trust components (2026-10-03) */
.calc-assumption-banner a { color: var(--color-primary-light); }

.tool-trust {
  margin-top: 1rem;
  padding: 0.85rem 1.1rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}
.tool-trust a { color: var(--color-primary-light); font-weight: 600; }
.tool-trust .sep { color: var(--color-border); margin: 0 0.35rem; }

.trust-summary {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.85rem;
  margin-bottom: 2rem;
}
@media (min-width: 640px) { .trust-summary { grid-template-columns: 1fr 1fr; } }
.trust-item {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-primary-light);
  border-radius: var(--radius-md);
  padding: 0.9rem 1rem;
}
.trust-q { font-weight: 700; color: var(--color-primary); font-size: 0.95rem; margin-bottom: 0.2rem; }
.trust-a { font-size: 0.9rem; color: var(--color-text-secondary); line-height: 1.5; }
.trust-a a, .page-meta a, .author-name a { color: var(--color-primary-light); font-weight: 600; }

.author-card { display: flex; gap: 1rem; align-items: flex-start; margin: 0.5rem 0 1rem; }
.author-card-lg { align-items: center; margin-bottom: 1.5rem; }
.author-avatar {
  flex-shrink: 0;
  width: 56px; height: 56px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
  color: #fff; font-weight: 800; font-size: 1.15rem;
  display: flex; align-items: center; justify-content: center;
}
.author-card-lg .author-avatar { width: 72px; height: 72px; font-size: 1.4rem; }
.legal-card .author-name { font-weight: 700; font-size: 1.05rem; margin-bottom: 0.1rem; }
.author-role, .legal-card .author-role { font-size: 0.9rem; color: var(--color-text-muted); font-weight: 600; margin-bottom: 0.5rem; }
.page-meta { font-size: 0.9rem; color: var(--color-text-muted); margin-bottom: 1.5rem; }
.site-footer .footer-bottom a { color: rgba(255, 255, 255, 0.85); }

.guide-article a:not(.btn):not(.related-card), .legal-card a { color: var(--color-primary-light); font-weight: 600; }
.legal-card > h2:first-child { margin-top: 0; }