:root {
  /* Core palette (enhanced for better accessibility) */
  --bg: #0f172a;            /* slate-900 */
  --surface: #1e293b;       /* slate-800 - improved contrast */
  --surface-2: #0f1729;     /* deep card */
  --surface-hover: #334155; /* slate-700 */
  --border: #334155;        /* slate-700 - better visibility */
  --border-light: #475569;  /* slate-600 */
  --text: #f1f5f9;          /* slate-100 - improved contrast */
  --text-secondary: #cbd5e1; /* slate-300 */
  --muted: #94a3b8;         /* slate-400 - better contrast */
  --accent: #60a5fa;        /* blue-400 */
  --accent-hover: #3b82f6;  /* blue-500 */
  --accent-light: #93c5fd;  /* blue-300 */
  --accent-contrast: #0b1020;
  --danger: #f87171;        /* red-400 - improved contrast */
  --danger-dark: #dc2626;   /* red-600 */
  --warn: #fbbf24;          /* amber-400 - improved contrast */
  --warn-dark: #f59e0b;     /* amber-500 */
  --ok: #34d399;            /* emerald-400 - improved contrast */
  --ok-dark: #10b981;       /* emerald-500 */
  --info: #38bdf8;          /* sky-400 */
  --focus: #22d3ee;         /* cyan-400 */

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.15);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 12px 30px rgba(0, 0, 0, 0.35);
  --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.45);
  
  /* Tables */
  --table-header: #1e293b;
  --table-row: #0f1729;
  --table-row-alt: #1a2332;
  --table-border: #334155;
  --table-hover: rgba(96, 165, 250, 0.08);

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

* {
  box-sizing: border-box;
}

body {
  background: radial-gradient(1400px 700px at 35% -10%, #1a2744 0%, var(--bg) 65%);
  color: var(--text);
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  line-height: 1.6;
  margin: 0;
  padding: 20px;
  min-height: 100vh;
}

/* Typography */
h1 { 
  color: var(--text); 
  font-size: 2rem; 
  font-weight: 800; 
  letter-spacing: -0.025em;
  margin: 0 0 8px 0;
  line-height: 1.2;
}

h2 { 
  color: var(--text); 
  font-size: 1.5rem; 
  font-weight: 700;
  letter-spacing: -0.015em;
  margin: 0 0 12px 0;
}

h3 { 
  color: var(--text); 
  font-size: 1.25rem; 
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 16px 0;
}

p {
  margin: 4px 0;
  line-height: 1.6;
}

.subtitle {
  color: var(--muted);
  font-size: 0.95rem;
  margin-top: 4px;
  font-weight: 500;
}

.muted { 
  color: var(--muted); 
  font-weight: 500; 
  letter-spacing: 0.3px;
  font-size: 0.875rem;
  text-transform: uppercase;
}

/* Layout */
.app-container {
  max-width: 1400px;
  margin: 0 auto;
}

.header-section {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}

/* Cards */
.card {
  background: linear-gradient(145deg, var(--surface) 0%, var(--surface-2) 100%);
  border-radius: 16px;
  padding: 24px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow-lg);
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
  position: relative;
  overflow: hidden;
}

.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(96, 165, 250, 0.3), transparent);
  opacity: 0;
  transition: opacity var(--transition-base);
}

.card:hover::before {
  opacity: 1;
}

.card:hover {
  border-color: var(--border-light);
  box-shadow: var(--shadow-xl);
  transform: translateY(-2px);
}

.card + .card { 
  margin-top: 24px; 
}

.card-compact {
  padding: 16px;
}

/* KPI Section */
.kpi { 
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin: 24px 0;
}

.kpi .tile {
  background: linear-gradient(135deg, rgba(96,165,250,0.05) 0%, rgba(16,185,129,0.03) 100%), var(--surface-2);
  border: 1px solid var(--border);
  padding: 20px 24px;
  border-radius: 14px;
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.kpi .tile::after {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  width: 100px;
  height: 100px;
  background: radial-gradient(circle, rgba(96, 165, 250, 0.08) 0%, transparent 70%);
  transform: translate(30%, -30%);
  transition: transform var(--transition-slow);
}

.kpi .tile:hover {
  border-color: var(--border-light);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  background: linear-gradient(135deg, rgba(96,165,250,0.08) 0%, rgba(16,185,129,0.05) 100%), var(--surface-2);
}

.kpi .tile:hover::after {
  transform: translate(20%, -20%);
}

.kpi .tile-label {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
}

.kpi .tile-icon {
  font-size: 1.25rem;
  opacity: 0.7;
}

.kpi .num { 
  font-size: 2rem; 
  font-weight: 800;
  line-height: 1;
  letter-spacing: -0.02em;
  position: relative;
  z-index: 1;
}

/* Badges */
.badge { 
  padding: 6px 12px; 
  border-radius: 12px; 
  font-size: 0.75rem;
  font-weight: 600;
  border: 1px solid transparent;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  letter-spacing: 0.025em;
  text-transform: uppercase;
  transition: all var(--transition-fast);
}

.badge.danger { 
  background: linear-gradient(135deg, rgba(248,113,113,0.2) 0%, rgba(239,68,68,0.15) 100%);
  color: var(--danger); 
  border-color: rgba(239,68,68,0.4);
}

.badge.warn { 
  background: linear-gradient(135deg, rgba(251,191,36,0.2) 0%, rgba(245,158,11,0.15) 100%);
  color: var(--warn); 
  border-color: rgba(245,158,11,0.4);
}

.badge.ok { 
  background: linear-gradient(135deg, rgba(52,211,153,0.2) 0%, rgba(16,185,129,0.15) 100%);
  color: var(--ok); 
  border-color: rgba(16,185,129,0.4);
}

.badge.info {
  background: linear-gradient(135deg, rgba(56,189,248,0.2) 0%, rgba(14,165,233,0.15) 100%);
  color: var(--info);
  border-color: rgba(56,189,248,0.4);
}

/* Links */
a, .link { 
  color: var(--accent); 
  text-decoration: none;
  transition: color var(--transition-fast);
  font-weight: 500;
}

a:hover, .link:hover { 
  color: var(--accent-light);
  text-decoration: underline;
}

/* Buttons */
button, .btn {
  appearance: none;
  border: 1px solid transparent;
  border-radius: 10px;
  background: linear-gradient(135deg, #2563eb 0%, #1e40af 100%);
  color: #ffffff;
  font-weight: 600;
  padding: 11px 20px;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: 0.9375rem;
  position: relative;
  overflow: hidden;
  box-shadow: 0 2px 8px rgba(37, 99, 235, 0.25);
}

button::before, .btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.1) 0%, transparent 100%);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

button:hover, .btn:hover { 
  box-shadow: 0 6px 20px rgba(96,165,250,0.4);
  border-color: var(--accent-light);
  transform: translateY(-2px);
}

button:hover::before, .btn:hover::before {
  opacity: 1;
}

button:active, .btn:active { 
  transform: translateY(0px);
  box-shadow: 0 2px 8px rgba(37, 99, 235, 0.25);
}

button:focus-visible, .btn:focus-visible { 
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

button:disabled, .btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

button:disabled:hover, .btn:disabled:hover {
  transform: none;
  box-shadow: none;
}

.btn-secondary {
  background: linear-gradient(135deg, var(--surface-hover) 0%, var(--surface) 100%);
  border-color: var(--border);
  box-shadow: var(--shadow-sm);
}

.btn-secondary:hover {
  border-color: var(--border-light);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.button-group {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

/* Upload area */
#upload-data {
  border-color: var(--border) !important;
  color: var(--muted);
  background: linear-gradient(135deg, rgba(96,165,250,0.1) 0%, rgba(96,165,250,0.03) 100%), var(--surface-2);
  transition: all var(--transition-base) !important;
  cursor: pointer;
  position: relative;
}

#upload-data::before {
  content: '📁';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -80%);
  font-size: 2rem;
  opacity: 0.3;
  transition: all var(--transition-base);
}

#upload-data:hover {
  border-color: var(--accent) !important;
  color: var(--accent-light);
  background: linear-gradient(135deg, rgba(96,165,250,0.15) 0%, rgba(96,165,250,0.05) 100%), var(--surface-2);
  box-shadow: 0 0 0 3px rgba(96, 165, 250, 0.1);
}

#upload-data:hover::before {
  transform: translate(-50%, -85%) scale(1.1);
  opacity: 0.5;
}

/* File info section */
#file-info {
  margin-top: 16px;
  padding: 12px;
  background: rgba(96, 165, 250, 0.05);
  border-radius: 8px;
  border: 1px solid rgba(96, 165, 250, 0.15);
}

#file-info:empty {
  display: none;
}

/* Tabs */
.dash-tabs {
  margin-bottom: 0 !important;
}

.dash-tabs .tab { 
  background: var(--surface-2) !important;
  border: 1px solid var(--border) !important;
  color: var(--muted) !important;
  border-bottom: none !important;
  border-top-left-radius: 10px;
  border-top-right-radius: 10px;
  padding: 10px 20px;
  font-weight: 600;
  transition: all var(--transition-fast) !important;
  margin-right: 4px;
}

.dash-tabs .tab:hover { 
  color: var(--text) !important;
  background: var(--surface) !important;
  border-color: var(--border-light) !important;
}

.dash-tabs .tab--selected { 
  background: var(--surface) !important;
  color: var(--text) !important;
  border-color: var(--accent) !important;
  border-bottom: 2px solid var(--accent) !important;
  position: relative;
}

#tab-content {
  background: var(--surface);
  padding: 20px;
  border-radius: 0 0 12px 12px;
  border: 1px solid var(--border);
  border-top: none;
  min-height: 200px;
}

/* DataTable styling */
.dash-table-container {
  border-radius: 8px;
  overflow: hidden;
}

.dash-table-container .dash-spreadsheet {
  background-color: transparent !important;
  border: 1px solid var(--table-border) !important;
  color: #ffffff !important;
  border-radius: 8px !important;
}

.dash-table-container .dash-spreadsheet-container table {
  border-collapse: separate !important;
  border-spacing: 0;
}

.dash-table-container .dash-spreadsheet .row {
  background-color: var(--table-row) !important;
  transition: background-color var(--transition-fast);
}

.dash-table-container .dash-spreadsheet .row:hover {
  background-color: var(--table-hover) !important;
}

.dash-table-container .dash-spreadsheet .row-odd {
  background-color: var(--table-row-alt) !important;
}

.dash-table-container .dash-spreadsheet .row-odd:hover {
  background-color: var(--table-hover) !important;
}

.dash-table-container .dash-spreadsheet .cell {
  background-color: transparent !important;
  border-color: var(--table-border) !important;
  color: var(--text) !important;
  padding: 10px 12px !important;
  transition: all var(--transition-fast);
}

.dash-table-container .dash-spreadsheet .cell.focused { 
  outline: 2px solid var(--focus) !important;
  outline-offset: -2px;
  background-color: rgba(34, 211, 238, 0.1) !important;
}

.dash-table-container .dash-spreadsheet .column-header-name {
  color: var(--text) !important;
  font-weight: 700 !important;
  font-size: 0.875rem;
  letter-spacing: 0.025em;
  text-transform: uppercase;
}

.dash-table-container .dash-spreadsheet .column-header {
  background-color: var(--table-header) !important;
  border-bottom: 2px solid var(--accent) !important;
  padding: 12px !important;
}

.dash-table-container .dash-spreadsheet .previous-page,
.dash-table-container .dash-spreadsheet .next-page {
  color: var(--accent) !important;
  transition: color var(--transition-fast);
}

.dash-table-container .dash-spreadsheet .previous-page:hover,
.dash-table-container .dash-spreadsheet .next-page:hover {
  color: var(--accent-light) !important;
}

/* Customer selector dropdown */
.form-group {
  margin-bottom: 20px;
}

.form-label {
  font-weight: 600;
  margin-bottom: 10px;
  display: block;
  color: var(--text);
  font-size: 0.9375rem;
  letter-spacing: 0.01em;
}

#customer-selector {
  background-color: var(--surface-2) !important;
  border: 1px solid var(--border) !important;
  border-radius: 10px !important;
  transition: all var(--transition-fast) !important;
}

#customer-selector:hover {
  border-color: var(--border-light) !important;
}

#customer-selector:focus {
  border-color: var(--accent) !important;
  box-shadow: 0 0 0 3px rgba(96, 165, 250, 0.15) !important;
}

/* Modern Dash Dropdown styling */
.dash-dropdown {
  color: #ffffff !important;
}

.dash-dropdown .Select-control {
  background-color: var(--surface-2) !important;
  border-color: var(--border) !important;
  color: #ffffff !important;
}

.dash-dropdown .Select-menu-outer {
  background-color: var(--surface) !important;
  border-color: var(--border) !important;
}

.dash-dropdown .Select-menu {
  background-color: var(--surface) !important;
}

.dash-dropdown .Select-option {
  background-color: transparent !important;
  color: #ffffff !important;
}

.dash-dropdown .Select-option:hover {
  background-color: rgba(96, 165, 250, 0.15) !important;
  color: #ffffff !important;
}

.dash-dropdown .Select-value {
  color: #ffffff !important;
}

.dash-dropdown .Select-value-label {
  color: #ffffff !important;
}

/* Newer Dash versions (React-Select v2+) */
div[class*="css-"][class*="control"] {
  background-color: var(--surface-2) !important;
  border-color: var(--border) !important;
}

div[class*="css-"][class*="menu"] {
  background-color: var(--surface) !important;
  border-color: var(--border) !important;
}

div[class*="css-"][class*="option"] {
  background-color: transparent !important;
  color: #ffffff !important;
}

div[class*="css-"][class*="option"]:hover {
  background-color: rgba(96, 165, 250, 0.15) !important;
  color: #ffffff !important;
}

div[class*="css-"][class*="singleValue"],
div[class*="css-"][class*="placeholder"],
div[class*="css-"][class*="input"] {
  color: #ffffff !important;
}

/* Dash dropdown styling (for older versions) */
.Select-control {
  background-color: var(--surface-2) !important;
  border: 1px solid var(--border) !important;
  border-radius: 10px !important;
  transition: all var(--transition-fast) !important;
  min-height: 42px !important;
}

.Select-control:hover {
  border-color: var(--border-light) !important;
}

.Select-menu-outer {
  background-color: var(--surface) !important;
  border: 1px solid var(--border) !important;
  border-radius: 10px !important;
  box-shadow: var(--shadow-lg) !important;
  margin-top: 4px !important;
}

.Select-option {
  background-color: transparent !important;
  color: #ffffff !important;
  padding: 10px 12px !important;
  transition: all var(--transition-fast) !important;
}

.Select-option:hover,
.Select-option.is-focused {
  background-color: rgba(96, 165, 250, 0.15) !important;
  color: #ffffff !important;
}

.Select-option.is-selected {
  background-color: rgba(96, 165, 250, 0.25) !important;
  color: #ffffff !important;
  font-weight: 600 !important;
}

.Select-value-label {
  color: var(--text) !important;
  font-weight: 500 !important;
}

.Select-placeholder {
  color: var(--muted) !important;
}

.Select-input > input {
  color: var(--text) !important;
}

/* Status messages */
.info {
  color: var(--info);
  font-weight: 600;
  margin: 6px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.info::before {
  content: 'ℹ️';
  font-size: 1rem;
}

.warn {
  color: var(--warn);
  font-weight: 600;
  margin: 6px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.warn::before {
  content: '⚠️';
  font-size: 1rem;
}

.success {
  color: var(--ok);
  font-weight: 600;
  margin: 6px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.success::before {
  content: '✅';
  font-size: 1rem;
}

.error-message {
  color: var(--danger);
  font-weight: 600;
  margin: 6px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.error-message::before {
  content: '❌';
  font-size: 1rem;
}

/* Loading spinner */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(15, 23, 42, 0.92);
  backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  animation: fadeIn var(--transition-base);
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.spinner {
  width: 60px;
  height: 60px;
  border: 4px solid var(--border);
  border-top-color: var(--accent);
  border-bottom-color: var(--accent-light);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  box-shadow: 0 0 20px rgba(96, 165, 250, 0.3);
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Progress bar animations */
#progress-bar {
  animation: progressPulse 1.5s ease-in-out infinite;
}

@keyframes progressPulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.8; }
}

#processing-status {
  animation: statusFade 0.5s ease-in-out;
}

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

/* Empty states */
.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--muted);
}

.empty-state-icon {
  font-size: 3rem;
  margin-bottom: 16px;
  opacity: 0.5;
}

.empty-state-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.empty-state-text {
  font-size: 0.9375rem;
  color: var(--muted);
}

/* Tooltips */
.tooltip-trigger {
  cursor: help;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: rgba(96, 165, 250, 0.2);
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 700;
  margin-left: 6px;
  transition: all var(--transition-fast);
}

.tooltip-trigger:hover {
  background: rgba(96, 165, 250, 0.3);
  transform: scale(1.1);
}

/* Scrollbar styling */
::-webkit-scrollbar {
  width: 12px;
  height: 12px;
}

::-webkit-scrollbar-track {
  background: var(--surface-2);
  border-radius: 6px;
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 6px;
  border: 2px solid var(--surface-2);
  transition: background var(--transition-fast);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--border-light);
}

/* Responsive design */
@media (max-width: 768px) {
  body {
    padding: 12px;
  }

  h1 {
    font-size: 1.75rem;
  }

  .card {
    padding: 16px;
  }

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

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

  .button-group button {
    width: 100%;
    margin-left: 0 !important;
  }
}

/* Accessibility improvements */
.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;
}

/* Focus visible for keyboard navigation */
*:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

/* Print styles */
@media print {
  body {
    background: white;
    color: black;
  }

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

  button {
    display: none;
  }
}