/* Calctool v2 — Main Stylesheet */

:root {
  --color-bg: #f5f7fa;
  --color-surface: #ffffff;
  --color-border: #dde1e6;
  --color-text: #1a1a2e;
  --color-text-secondary: #555;
  --color-text-muted: #8b8fa3;
  --color-primary: #2563eb;
  --color-primary-light: #dbeafe;
  --color-error: #dc2626;
  --color-error-light: #fef2f2;
  --color-highlight-dep: #fef9c3;
  --color-highlight-dependent: #dbeafe;
  --color-highlight-self: #e0f2fe;
  --color-highlight-input-text: #92400e;
  --color-highlight-output-text: #1d4ed8;
  --radius: 6px;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 2px 8px rgba(0,0,0,0.1);

  /* Surfaces */
  --color-on-primary: #fff;
  --color-input-row-bg: #fff;
  --color-unit-selector-bg: #f9fafb;
  --color-output-bg: #f3f4f6;
  --color-alt-row: #f8f9fb;
  --color-chemical-card-bg: #f8fafc;
  --color-chemical-card-border: #e2e8f0;

  /* Results section */
  --color-results-bg: #fafaff;
  --color-results-border: #c7d2fe;
  --color-results-header: #eef2ff;
  --color-results-header-hover: #e0e7ff;
  --color-hero-border: #e0e7ff;

  /* Badges: pinned / warning (amber) */
  --color-pinned-text: #92400e;
  --color-pinned-bg: #fef3c7;
  --color-pinned-hover-bg: #fde68a;
  --color-pinned-hover-text: #78350f;
  --color-pinned-border: #f59e0b;
  --color-pinned-row-bg: #fffbeb;

  /* Badges: source (green) */
  --color-source-bg: #f0fdf4;
  --color-source-border: #bbf7d0;

  /* Badges: auto (teal) */
  --color-auto-text: #0e7490;
  --color-auto-bg: #e0f2fe;

  /* Badges: range (teal/cyan) */
  --color-range-text: #0e7490;
  --color-range-bg: #ecfeff;

  /* Badges: bypassed / method-chip (gray) */
  --color-chip-bg: #f3f4f6;

  /* Phase badges */
  --color-phase-liquid-bg: #dbeafe;
  --color-phase-liquid-text: #1d4ed8;
  --color-phase-vapor-bg: #ffedd5;
  --color-phase-vapor-text: #c2410c;
  --color-phase-gas-bg: #fef2f2;
  --color-phase-gas-text: #dc2626;

  /* Regime badges */
  --color-regime-laminar-bg: #d1fae5;
  --color-regime-laminar-text: #065f46;
  --color-regime-transitional-bg: #fef3c7;
  --color-regime-transitional-text: #92400e;
  --color-regime-turbulent-bg: #fee2e2;
  --color-regime-turbulent-text: #991b1b;

  /* Tooltip */
  --color-tooltip-bg: #1f2937;
  --color-tooltip-text: #fff;

  /* Shimmer */
  --color-shimmer-base: #e5e7eb;
  --color-shimmer-highlight: #f3f4f6;
}

/* ─── Dark theme ─── */
[data-theme="dark"] {
  color-scheme: dark;
  --color-bg: #0f1117;
  --color-surface: #1a1d27;
  --color-border: #2e3244;
  --color-text: #e2e4ea;
  --color-text-secondary: #a0a4b8;
  --color-text-muted: #6b7084;
  --color-primary: #5b8def;
  --color-primary-light: #1e2a4a;
  --color-error: #f87171;
  --color-error-light: #3b1c1c;
  --color-highlight-dep: #3b3520;
  --color-highlight-dependent: #1e2a4a;
  --color-highlight-self: #1a2e3e;
  --color-highlight-input-text: #fbbf24;
  --color-highlight-output-text: #93bbfd;
  --shadow: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 2px 8px rgba(0,0,0,0.4);

  --color-on-primary: #fff;
  --color-input-row-bg: #1e2130;
  --color-unit-selector-bg: #252838;
  --color-output-bg: #252838;
  --color-alt-row: #1e2130;
  --color-chemical-card-bg: #1e2130;
  --color-chemical-card-border: #2e3244;

  --color-results-bg: #181b28;
  --color-results-border: #3b4060;
  --color-results-header: #1e2240;
  --color-results-header-hover: #252850;
  --color-hero-border: #3b4060;

  --color-pinned-text: #fbbf24;
  --color-pinned-bg: #3b3520;
  --color-pinned-hover-bg: #4a4228;
  --color-pinned-hover-text: #fcd34d;
  --color-pinned-border: #d97706;
  --color-pinned-row-bg: #2a2515;

  --color-source-bg: #162317;
  --color-source-border: #2d4a2e;

  --color-auto-text: #67e8f9;
  --color-auto-bg: #162a35;

  --color-range-text: #67e8f9;
  --color-range-bg: #162a35;

  --color-chip-bg: #252838;

  --color-phase-liquid-bg: #1e2a4a;
  --color-phase-liquid-text: #93bbfd;
  --color-phase-vapor-bg: #3b2a15;
  --color-phase-vapor-text: #fdba74;
  --color-phase-gas-bg: #3b1c1c;
  --color-phase-gas-text: #fca5a5;

  --color-regime-laminar-bg: #162317;
  --color-regime-laminar-text: #6ee7b7;
  --color-regime-transitional-bg: #3b3520;
  --color-regime-transitional-text: #fbbf24;
  --color-regime-turbulent-bg: #3b1c1c;
  --color-regime-turbulent-text: #fca5a5;

  --color-tooltip-bg: #e2e4ea;
  --color-tooltip-text: #1a1d27;

  --color-shimmer-base: #252838;
  --color-shimmer-highlight: #2e3244;
}

/* Dark mode SVG caret overrides */
[data-theme="dark"] .unit-selector,
[data-theme="dark"] .method-selector,
[data-theme="dark"] .hero-unit-select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='8' height='5' viewBox='0 0 8 5'%3E%3Cpath d='M0 0l4 5 4-5z' fill='%236b7084'/%3E%3C/svg%3E");
}

[data-theme="dark"] .unit-selector:hover,
[data-theme="dark"] .method-selector:hover,
[data-theme="dark"] .hero-unit-select:hover {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='8' height='5' viewBox='0 0 8 5'%3E%3Cpath d='M0 0l4 5 4-5z' fill='%235b8def'/%3E%3C/svg%3E");
}

[data-theme="dark"] .chemical-search {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%236b7084' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='11' cy='11' r='8'/%3E%3Cline x1='21' y1='21' x2='16.65' y2='16.65'/%3E%3C/svg%3E");
}

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

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
}

/* ─── Accent strip ─── */
.accent-strip {
  height: 4px;
  background: linear-gradient(90deg, #2563eb, #4f46e5, #7c3aed);
}

/* ─── Header ─── */
.app-header {
  padding: 1.5rem 2rem 1rem;
  max-width: 900px;
  margin: 0 auto;
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
}

.app-header h1 {
  margin: 0;
  font-size: 1.5rem;
  font-weight: 600;
}

.version-badge {
  display: inline-block;
  padding: 0.125rem 0.5rem;
  font-size: 0.6875rem;
  font-weight: 600;
  color: var(--color-primary);
  background: var(--color-primary-light);
  border-radius: 9999px;
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.app-header .subtitle {
  margin: 0;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  flex: 1;
}

/* ─── Header controls (theme toggle + share + unit toggle) ─── */
.header-controls {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-shrink: 0;
}

/* ─── Theme toggle button ─── */
.theme-toggle-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  border: 1px solid var(--color-border);
  border-radius: 50%;
  background: transparent;
  color: var(--color-text-muted);
  font-size: 0.875rem;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
  flex-shrink: 0;
  padding: 0;
  font-family: inherit;
}

.theme-toggle-btn svg {
  display: block;
}

.theme-toggle-btn.theme-sun {
  color: #e8a020;
  filter: drop-shadow(0 0 4px rgba(245, 180, 50, 0.5));
}

.theme-toggle-btn.theme-moon {
  color: #b0c4de;
  filter: drop-shadow(0 0 4px rgba(176, 210, 255, 0.45));
}

.theme-toggle-btn:hover {
  background: var(--color-bg);
  border-color: var(--color-text-muted);
}

.theme-toggle-btn.theme-sun:hover {
  color: #d4911a;
  filter: drop-shadow(0 0 6px rgba(245, 180, 50, 0.7));
}

.theme-toggle-btn.theme-moon:hover {
  color: #cde0f5;
  filter: drop-shadow(0 0 6px rgba(176, 210, 255, 0.65));
}

/* ─── Share button ─── */
.share-btn {
  padding: 0.25rem 0.75rem;
  font-size: 0.75rem;
  font-weight: 600;
  font-family: inherit;
  border: 1px solid var(--color-border);
  border-radius: 9999px;
  background: transparent;
  color: var(--color-text-muted);
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
  white-space: nowrap;
  flex-shrink: 0;
}

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

.share-btn.copied {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

/* ─── Unit system toggle ─── */
.unit-system-toggle {
  display: flex;
  border: 1px solid var(--color-border);
  border-radius: 9999px;
  overflow: hidden;
  flex-shrink: 0;
}

.unit-system-btn {
  padding: 0.25rem 0.75rem;
  font-size: 0.75rem;
  font-weight: 600;
  font-family: inherit;
  border: none;
  background: transparent;
  color: var(--color-text-muted);
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.unit-system-btn:hover {
  background: var(--color-bg);
  color: var(--color-text-secondary);
}

.unit-system-btn.active {
  background: var(--color-primary);
  color: var(--color-on-primary);
}

/* ─── Sections container ─── */
.sections {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 2rem 3rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* ─── Section card ─── */
.section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.section-accent-top {
  height: 3px;
}

/* ─── Section header ─── */
.section-header {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  padding: 0.75rem 1rem;
  cursor: pointer;
  user-select: none;
  border-bottom: 1px solid transparent;
  transition: background 0.15s;
}

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

.step-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 1.5rem;
  height: 1.5rem;
  border-radius: 50%;
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--color-on-primary);
  flex-shrink: 0;
}

.section-header h2 {
  margin: 0;
  font-size: 1rem;
  font-weight: 600;
  flex: 1;
}

.toggle-label {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  white-space: nowrap;
  transition: color 0.15s;
}

.toggle-icon {
  font-size: 0.625rem;
  color: var(--color-text-muted);
  transition: transform 0.2s;
}

.section.expanded .toggle-icon {
  transform: rotate(90deg);
}

.section.expanded .section-header {
  border-bottom-color: var(--color-border);
}

/* ─── Results section distinct look ─── */
.section[data-section-id="results"] {
  background: var(--color-results-bg);
  border-color: var(--color-results-border);
}

.section[data-section-id="results"] .section-header {
  background: var(--color-results-header);
}

.section[data-section-id="results"] .section-header:hover {
  background: var(--color-results-header-hover);
}

/* ─── Section body ─── */
.section-body {
  padding: 0.75rem 1rem;
}

/* ─── Detail fields: animated expand/collapse ─── */
.detail-fields {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, opacity 0.2s ease;
  opacity: 0;
  margin-top: 0;
  padding-top: 0;
  border-top: 1px solid transparent;
}

.section.expanded .detail-fields {
  max-height: 1200px;
  opacity: 1;
  margin-top: 0.5rem;
  padding-top: 0.5rem;
  border-top-color: var(--color-border);
}

/* ─── Fields container ─── */
.fields {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

/* Alternating subtle backgrounds in detail sections */
.detail-fields .field-row:nth-child(even) {
  background: var(--color-alt-row);
  border-radius: 4px;
}

/* ─── Field row ─── */
.field-row {
  position: relative;
  display: grid;
  grid-template-columns: 200px 1fr auto;
  gap: 0.5rem;
  align-items: center;
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
  transition: background 0.3s ease;
}

/* ─── Field label ─── */
.field-label {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.field-input {
  min-width: 0;
}

/* ─── Input controls ─── */
.field-input-control {
  width: 100%;
  padding: 0.375rem 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
  transition: border-color 0.15s, box-shadow 0.15s;
}

.field-input-control:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px var(--color-primary-light);
}

.number-input {
  max-width: 140px;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

/* ─── Input-group: fused value + unit ─── */
.input-group {
  display: inline-flex;
  align-items: center;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-surface);
  transition: border-color 0.15s, box-shadow 0.15s;
  max-width: 220px;
}

.input-group:focus-within {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px var(--color-primary-light);
}

.input-group .field-input-control {
  border: none;
  border-radius: 4px 0 0 4px;
  box-shadow: none;
}

.input-group .field-input-control:focus {
  box-shadow: none;
  border-color: transparent;
}

.input-group .unit-selector {
  border: none;
  border-left: 1px solid var(--color-border);
  border-radius: 0 4px 4px 0;
  background: var(--color-unit-selector-bg);
  margin-left: 0;
  padding: 0.375rem 0.375rem;
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  cursor: pointer;
  white-space: nowrap;
}

.input-group .unit-selector:focus {
  outline: none;
  color: var(--color-primary);
}

/* ─── Output-group: value + ghost unit inline ─── */
.output-group {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}

.chemical-search {
  width: 300px;
  max-width: 100%;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='14' height='14' viewBox='0 0 24 24' fill='none' stroke='%238b8fa3' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='11' cy='11' r='8'/%3E%3Cline x1='21' y1='21' x2='16.65' y2='16.65'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 8px center;
  padding-right: 28px;
}

.chemical-search-wrapper {
  position: relative;
}

.chem-dropdown {
  position: fixed;
  max-height: 240px;
  overflow-y: auto;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 0 0 var(--radius) var(--radius);
  box-shadow: var(--shadow-md);
  z-index: 100;
}

.chem-dropdown-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.375rem 0.5rem;
  cursor: pointer;
  transition: background 0.1s;
  white-space: nowrap;
}

.chem-dropdown-item:hover,
.chem-dropdown-item.active {
  background: var(--color-primary-light);
}

.chem-dropdown-item .chem-name {
  font-size: 0.8125rem;
  color: var(--color-text);
}

.chem-dropdown-item .chem-cas {
  font-size: 0.6875rem;
  color: var(--color-text-muted);
  margin-left: 1rem;
  flex-shrink: 0;
}

.chem-dropdown-empty {
  padding: 0.5rem;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  font-style: italic;
}

.selection-dropdown {
  max-width: 240px;
}

/* ─── Visual distinction: input rows ─── */
.field-row.row-input {
  border-left: 3px solid var(--color-primary-light);
  background: var(--color-input-row-bg);
}

/* ─── Visual distinction: overridable (pinned) rows ─── */
.field-row.row-override {
  border-left: 3px solid transparent;
}

.field-row.row-override.is-pinned {
  border-left-color: var(--color-pinned-border);
  background: var(--color-pinned-row-bg);
}

.pinned-badge {
  margin-left: 0.375rem;
  padding: 0.0625rem 0.375rem;
  font-size: 0.625rem;
  font-weight: 600;
  color: var(--color-pinned-text);
  background: var(--color-pinned-bg);
  border-radius: 9999px;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.pinned-badge:hover {
  background: var(--color-pinned-hover-bg);
  color: var(--color-pinned-hover-text);
}

.override-input::placeholder {
  color: var(--color-text-muted);
  font-style: italic;
}

.bypassed-badge {
  margin-left: 0.375rem;
  padding: 0.0625rem 0.3rem;
  font-size: 0.5625rem;
  font-weight: 500;
  color: var(--color-text-muted);
  background: var(--color-chip-bg);
  border-radius: 3px;
  text-transform: uppercase;
  cursor: default;
}

/* ─── Source citation badge ─── */
.source-badge {
  margin-left: 0.375rem;
  padding: 0.0625rem 0.3rem;
  font-size: 0.5625rem;
  font-weight: 500;
  font-style: italic;
  color: var(--color-text-muted);
  background: var(--color-source-bg);
  border: 1px solid var(--color-source-border);
  border-radius: 3px;
  cursor: help;
}

/* ─── Source popover ─── */
.source-popover {
  position: fixed;
  z-index: 200;
  max-width: 360px;
  padding: 0.625rem 0.75rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  font-size: 0.8125rem;
  line-height: 1.45;
  color: var(--color-text);
  pointer-events: auto;
  opacity: 0;
  transform: translateY(4px);
  transition: opacity 0.15s ease, transform 0.15s ease;
}

.source-popover.visible {
  opacity: 1;
  transform: translateY(0);
}

.source-popover-method {
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.source-popover-description {
  margin-bottom: 0.375rem;
  color: var(--color-text-secondary);
}

.source-popover-assumption {
  margin-bottom: 0.375rem;
  font-style: italic;
  color: var(--color-text-secondary);
}

.source-popover-range {
  margin-bottom: 0.375rem;
  font-size: 0.75rem;
  color: var(--color-range-text);
  background: var(--color-range-bg);
  display: inline-block;
  padding: 0.125rem 0.375rem;
  border-radius: 3px;
}

.source-popover-reference {
  font-size: 0.6875rem;
  color: var(--color-text-muted);
  border-top: 1px solid var(--color-border);
  padding-top: 0.375rem;
  margin-top: 0.25rem;
}

/* ─── Warning badge (extrapolated range) ─── */
.warning-badge {
  margin-left: 0.375rem;
  padding: 0.0625rem 0.3rem;
  font-size: 0.5625rem;
  font-weight: 500;
  color: var(--color-pinned-text);
  background: var(--color-pinned-bg);
  border-radius: 9999px;
  cursor: help;
}

/* ─── Method selector group (selector + status badge inline) ─── */
.method-selector-group {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

/* ─── Method status badge (auto / pinned) ─── */
.method-status-badge {
  padding: 0.0625rem 0.3rem;
  font-size: 0.5625rem;
  font-weight: 500;
  border-radius: 9999px;
  cursor: help;
  white-space: nowrap;
}

.method-status-badge.status-auto {
  color: var(--color-auto-text);
  background: var(--color-auto-bg);
}

.method-status-badge.status-pinned {
  color: var(--color-pinned-text);
  background: var(--color-pinned-bg);
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.method-status-badge.status-pinned:hover {
  background: var(--color-pinned-hover-bg);
  color: var(--color-pinned-hover-text);
}

.field-row.has-warning {
  border-left: 2px solid var(--color-pinned-border);
}

/* ─── Visual distinction: output rows ─── */
.field-row.row-output .field-output {
  font-family: 'SF Mono', 'Cascadia Code', 'Consolas', monospace;
  background: var(--color-output-bg);
  border-radius: 4px;
  padding: 0.25rem 0.5rem;
}

/* ─── Visual distinction: lookup rows ─── */
.field-row.row-lookup .field-output {
  font-style: italic;
  color: var(--color-text-secondary);
}

/* ─── Output display ─── */
.field-output {
  font-size: 0.875rem;
  font-variant-numeric: tabular-nums;
  padding: 0.375rem 0.5rem;
  min-width: 100px;
  text-align: right;
}

.field-output.error {
  color: var(--color-error);
  font-size: 0.75rem;
}

/* Empty/pending output: gray dash */
.field-output.empty {
  color: var(--color-text-muted);
}

/* ─── Dependency error hint below output ─── */
.field-error-hint {
  font-size: 0.6875rem;
  color: var(--color-text-muted);
  font-style: italic;
  margin-top: 0.125rem;
}

.field-error-link {
  color: var(--color-primary);
  cursor: pointer;
  text-decoration: underline dotted;
  font-size: 0.6875rem;
  font-style: italic;
  margin-top: 0.125rem;
  background: none;
  border: none;
  padding: 0;
  font-family: inherit;
}

.field-error-link:hover {
  text-decoration: underline solid;
}

@keyframes field-highlight {
  0% { background-color: rgba(37, 99, 235, 0.12); }
  100% { background-color: transparent; }
}
.field-row.highlight { animation: field-highlight 1.5s ease-out; }

/* ─── Ghost caret for appearance:none selects ─── */
.unit-selector,
.method-selector,
.hero-unit-select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='8' height='5' viewBox='0 0 8 5'%3E%3Cpath d='M0 0l4 5 4-5z' fill='%238b8fa3'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 2px center;
  padding-right: 14px;
}

.unit-selector:hover,
.method-selector:hover,
.hero-unit-select:hover {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='8' height='5' viewBox='0 0 8 5'%3E%3Cpath d='M0 0l4 5 4-5z' fill='%232563eb'/%3E%3C/svg%3E");
}

/* Input-group unit selector: visible button style, no ghost caret */
.input-group .unit-selector,
.input-group .unit-selector:hover {
  background-image: none;
  padding-right: 0.375rem;
}

/* ─── Unit selector: ghost style (standalone / output rows) ─── */
.unit-selector {
  appearance: none;
  -webkit-appearance: none;
  border: none;
  background-color: transparent;
  font-size: 0.75rem;
  font-family: inherit;
  color: var(--color-text-muted);
  cursor: pointer;
  padding: 0.125rem 14px 0.125rem 0.25rem;
  border-bottom: 1px dotted transparent;
  transition: color 0.15s, border-color 0.15s;
}

.unit-selector:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.unit-selector:focus {
  outline: none;
  color: var(--color-primary);
}

/* ─── Method selector: ghost style ─── */
.method-selector {
  appearance: none;
  -webkit-appearance: none;
  border: none;
  background-color: transparent;
  padding: 0.125rem 14px 0.125rem 0.25rem;
  font-size: 0.6875rem;
  font-family: inherit;
  color: var(--color-text-muted);
  cursor: pointer;
  max-width: 180px;
  border-bottom: 1px dotted transparent;
  transition: color 0.15s, border-color 0.15s;
}

.method-selector:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.method-selector:focus {
  outline: none;
  color: var(--color-primary);
}

/* ─── Method label (single-method, static) ─── */
.method-label {
  font-size: 0.6875rem;
  font-family: inherit;
  color: var(--color-text-muted);
}

/* ─── Phase badge ─── */
.phase-badge {
  display: inline-block;
  padding: 0.125rem 0.5rem;
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 9999px;
  letter-spacing: 0.02em;
  text-transform: capitalize;
}

.phase-badge.phase-liquid {
  background: var(--color-phase-liquid-bg);
  color: var(--color-phase-liquid-text);
}

.phase-badge.phase-vapor {
  background: var(--color-phase-vapor-bg);
  color: var(--color-phase-vapor-text);
}

.phase-badge.phase-gas {
  background: var(--color-phase-gas-bg);
  color: var(--color-phase-gas-text);
}

/* ─── Inline primary: flex row for compact sections ─── */
.inline-primary {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.inline-primary .field-row {
  flex-shrink: 0;
}

/* ─── Fluid section: search + card on one line ─── */
.fluid-primary-row {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.fluid-primary-row .field-row {
  flex-shrink: 0;
}

/* ─── Chemical summary card ─── */
.chemical-card {
  display: flex;
  gap: 1.5rem;
  padding: 0.375rem 0.75rem;
  background: var(--color-chemical-card-bg);
  border: 1px solid var(--color-chemical-card-border);
  border-radius: var(--radius);
  font-size: 0.8125rem;
  flex: 1;
  min-width: 0;
}

.chemical-card-item {
  display: flex;
  flex-direction: column;
  gap: 0.0625rem;
}

.chemical-card-label {
  font-size: 0.6875rem;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  font-weight: 500;
}

.chemical-card-value {
  font-weight: 600;
  color: var(--color-text);
}

/* ─── Fluid detail: 2-column grid for lookup fields ─── */
.section[data-section-id="fluid"] .detail-fields {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
}

/* ─── Results hero layout ─── */
.results-hero {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  margin-bottom: 0.75rem;
}

.hero-item {
  flex: 1;
  min-width: 180px;
  padding: 0.75rem 1rem;
  background: var(--color-surface);
  border: 1px solid var(--color-hero-border);
  border-radius: var(--radius);
  text-align: center;
}

.hero-label {
  font-size: 0.875rem;
  color: var(--color-text);
  font-weight: 500;
  margin-bottom: 0.25rem;
}

.hero-value {
  font-size: 1.5rem;
  font-weight: 700;
  font-family: 'SF Mono', 'Cascadia Code', 'Consolas', monospace;
  font-variant-numeric: tabular-nums;
  color: var(--color-text);
  line-height: 1.2;
}

.hero-unit {
  font-size: 0.75rem;
  font-weight: 400;
  color: var(--color-text-muted);
  margin-top: 0.125rem;
}

.hero-unit-select {
  appearance: none;
  -webkit-appearance: none;
  border: none;
  background-color: transparent;
  font-size: 0.75rem;
  font-family: inherit;
  color: var(--color-text-muted);
  cursor: pointer;
  padding: 0.125rem 14px 0.125rem 0.25rem;
  border-bottom: 1px dotted transparent;
  transition: color 0.15s, border-color 0.15s;
  text-align: center;
}

.hero-unit-select:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.hero-unit-select:focus {
  outline: none;
  color: var(--color-primary);
}

.hero-value-row {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 0.375rem;
}

.hero-copy-btn {
  appearance: none;
  border: none;
  background: none;
  color: var(--color-text-muted);
  font-size: 0.625rem;
  font-family: inherit;
  cursor: pointer;
  padding: 0.125rem 0.25rem;
  border-radius: 3px;
  opacity: 0;
  transition: opacity 0.15s, color 0.15s, background-color 0.15s;
  white-space: nowrap;
  align-self: center;
}

.hero-item:hover .hero-copy-btn {
  opacity: 1;
}

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

.hero-copy-btn.copied {
  opacity: 1;
  color: var(--color-primary);
}

.hero-value.empty {
  color: var(--color-text-muted);
  font-size: 1.25rem;
}

/* ─── Flow regime badge ─── */
.regime-badge {
  display: inline-block;
  margin-top: 0.25rem;
  padding: 0.0625rem 0.5rem;
  font-size: 0.6875rem;
  font-weight: 600;
  border-radius: 9999px;
  letter-spacing: 0.02em;
}

.regime-badge.regime-laminar {
  background: var(--color-regime-laminar-bg);
  color: var(--color-regime-laminar-text);
}

.regime-badge.regime-transitional {
  background: var(--color-regime-transitional-bg);
  color: var(--color-regime-transitional-text);
}

.regime-badge.regime-turbulent {
  background: var(--color-regime-turbulent-bg);
  color: var(--color-regime-turbulent-text);
}

/* ─── Friction method chip ─── */
.method-chip {
  display: inline-block;
  margin-top: 0.125rem;
  padding: 0.0625rem 0.375rem;
  font-size: 0.625rem;
  color: var(--color-text-muted);
  background: var(--color-chip-bg);
  border-radius: 4px;
}

/* ─── SCF annotation (mass-equivalent line) ─── */
.scf-annotation {
  font-size: 0.6875rem;
  color: var(--color-text-muted);
  margin-top: 0.125rem;
}

/* ─── Hover highlighting (with fade transition) ─── */
.field-row.highlight-dependency,
.hero-item.highlight-dependency {
  background: var(--color-highlight-dep) !important;
}

.field-row.highlight-dependent,
.hero-item.highlight-dependent {
  background: var(--color-highlight-dependent) !important;
}

.field-row.highlight-self,
.hero-item.highlight-self,
.fittings-list-item.highlight-self {
  background: var(--color-highlight-self) !important;
}

/* ─── Hover highlight labels ─── */
.highlight-label {
  margin-left: 0.375rem;
  font-size: 0.5625rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  pointer-events: none;
}

.highlight-label-input {
  color: var(--color-highlight-input-text);
}

.highlight-label-output {
  color: var(--color-highlight-output-text);
}

/* ─── Invalid input: red border ─── */
.field-row.input-invalid .field-input-control {
  border-color: var(--color-error);
  box-shadow: 0 0 0 2px var(--color-error-light);
}

.field-row.input-invalid .input-group {
  border-color: var(--color-error);
  box-shadow: 0 0 0 2px var(--color-error-light);
}

/* ─── Error tooltip ─── */
.error-tooltip {
  position: relative;
  cursor: help;
}

.error-tooltip .error-tooltip-text {
  display: none;
  position: absolute;
  bottom: 100%;
  right: 0;
  margin-bottom: 4px;
  padding: 0.375rem 0.625rem;
  background: var(--color-tooltip-bg);
  color: var(--color-tooltip-text);
  font-size: 0.6875rem;
  border-radius: 4px;
  white-space: nowrap;
  z-index: 10;
  pointer-events: none;
}

.error-tooltip:hover .error-tooltip-text {
  display: block;
}

/* ─── Shimmer loading skeleton ─── */
.loading-skeleton {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem;
}

.shimmer-header {
  height: 2rem;
  width: 280px;
  background: linear-gradient(90deg, var(--color-shimmer-base) 25%, var(--color-shimmer-highlight) 50%, var(--color-shimmer-base) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: 4px;
  margin-bottom: 0.5rem;
}

.shimmer-subtitle {
  height: 1rem;
  width: 200px;
  background: linear-gradient(90deg, var(--color-shimmer-base) 25%, var(--color-shimmer-highlight) 50%, var(--color-shimmer-base) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: 4px;
  margin-bottom: 1.5rem;
}

.shimmer-card {
  height: 52px;
  background: linear-gradient(90deg, var(--color-shimmer-base) 25%, var(--color-shimmer-highlight) 50%, var(--color-shimmer-base) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius);
  margin-bottom: 1rem;
}

@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ─── Valid/invalid states ─── */
.field-row.invalid .field-output {
  color: var(--color-error);
}

/* ─── Responsive ─── */
@media (max-width: 640px) {
  .app-header {
    padding-left: 1rem;
    padding-right: 1rem;
    flex-direction: column;
    gap: 0.25rem;
  }

  .sections {
    padding-left: 1rem;
    padding-right: 1rem;
  }

  .field-row {
    grid-template-columns: 1fr;
    gap: 0.25rem;
  }

  .input-group {
    max-width: 100%;
  }

  .field-label {
    font-weight: 600;
  }

  .number-input,
  .chemical-search,
  .selection-dropdown {
    max-width: 100%;
  }

  .results-hero {
    flex-direction: column;
  }

  .hero-item {
    min-width: 0;
  }

  .inline-primary {
    flex-direction: column;
    align-items: stretch;
  }

  .fluid-primary-row {
    flex-direction: column;
    align-items: stretch;
  }

  .section[data-section-id="fluid"] .detail-fields {
    grid-template-columns: 1fr;
  }

  .chemical-card {
    flex-direction: column;
    gap: 0.5rem;
  }

  .header-controls {
    justify-content: flex-end;
    width: 100%;
  }

  .fittings-editor {
    padding-left: 0.5rem;
  }
}

/* ─── Fittings editor ─── */
.fittings-editor {
  padding: 0.25rem 0.5rem 0.25rem calc(200px + 1rem);
}

.fittings-method-group {
  margin-bottom: 0.25rem;
}

.fittings-add-row {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  flex-wrap: wrap;
}

.fittings-select {
  flex: 1 1 180px;
  min-width: 0;
  padding: 0.375rem 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
}

.fittings-custom-name {
  flex: 1 1 120px;
  min-width: 0;
  padding: 0.375rem 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
}

.fittings-custom-k {
  width: 72px;
  padding: 0.375rem 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  font-family: inherit;
  text-align: right;
  background: var(--color-surface);
  color: var(--color-text);
}

.fittings-qty {
  width: 52px;
  padding: 0.375rem 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  font-family: inherit;
  text-align: center;
  background: var(--color-surface);
  color: var(--color-text);
}

.fittings-add-btn {
  padding: 0.375rem 0.625rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-size: 0.875rem;
  font-family: inherit;
  background: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
  transition: background 0.15s;
}

.fittings-add-btn:hover {
  background: var(--color-alt-row);
}

.fittings-custom-row {
  display: none;
  align-items: center;
  gap: 0.375rem;
  flex-wrap: wrap;
  margin-top: 0.25rem;
}

.fittings-custom-row.visible {
  display: flex;
}

.fittings-list {
  display: flex;
  flex-direction: column;
  gap: 0.125rem;
  margin-top: 0.375rem;
}

.fittings-list-item {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  padding: 0.25rem 0.375rem;
  font-size: 0.875rem;
  border-radius: 3px;
  background: var(--color-alt-row);
}

.fittings-item-name {
  flex: 1 1 auto;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  color: var(--color-text);
}

.fittings-item-qty {
  width: 42px;
  padding: 0.125rem 0.25rem;
  border: 1px solid var(--color-border);
  border-radius: 3px;
  font-size: 0.875rem;
  font-family: inherit;
  text-align: center;
  background: var(--color-surface);
  color: var(--color-text);
}

.fittings-item-k {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  white-space: nowrap;
  min-width: 60px;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

.fittings-remove-btn {
  padding: 0 0.375rem;
  border: none;
  background: none;
  color: var(--color-text-muted);
  font-size: 1rem;
  cursor: pointer;
  line-height: 1;
  border-radius: 3px;
  transition: color 0.15s, background 0.15s;
}

.fittings-remove-btn:hover {
  color: #dc2626;
  background: rgba(220, 38, 38, 0.08);
}

/* ─── Hero pressure-drop breakdown ─── */
.hero-dp-breakdown {
  margin-top: 0.25rem;
  font-size: 0.75rem;
  color: var(--color-text-muted);
  line-height: 1.4;
  font-variant-numeric: tabular-nums;
}

/* ─── Print stylesheet ─── */
@media print {
  .accent-strip,
  .version-badge,
  .toggle-icon,
  .toggle-label,
  .method-selector,
  .unit-selector,
  .section-header {
    cursor: default;
  }

  .field-input-control,
  .selection-dropdown,
  .chemical-search,
  .method-selector,
  .theme-toggle-btn,
  .share-btn {
    display: none;
  }

  .section {
    box-shadow: none;
    border: 1px solid #ccc;
    break-inside: avoid;
  }

  .detail-fields {
    max-height: none !important;
    opacity: 1 !important;
    overflow: visible !important;
  }

  .section-body {
    display: block;
  }

  body {
    background: #fff;
  }

  .field-row {
    grid-template-columns: 200px 1fr;
  }

  .unit-selector,
  .hero-unit-select {
    appearance: auto;
    -webkit-appearance: auto;
  }

  .field-row.row-input .print-value {
    display: block;
  }
}