:root {
  /* Colors - Slate & Indigo Theme */
  --bg-app: #0f172a;
  --bg-panel: #1e293b;
  --bg-card: #334155;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --accent-primary: #6366f1;
  --accent-hover: #4f46e5;
  --accent-secondary: #334155;
  --accent-secondary-hover: #475569;
  --border-color: #334155;
  --success: #10b981;
  
  /* Spacing & Radius */
  --radius-lg: 16px;
  --radius-md: 8px;
  --radius-sm: 4px;
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
}

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

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background-color: var(--bg-app);
  color: var(--text-primary);
  line-height: 1.5;
  min-height: 100vh;
}

/* Layout */
.app-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--spacing-md);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

/* Header */
.app-header {
  display: flex;
  align-items: center;
  padding: var(--spacing-md) 0;
  border-bottom: 1px solid var(--border-color);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  color: var(--accent-primary);
}

.logo h1 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.025em;
}

/* Main Content */
.main-content {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: var(--spacing-xl);
  align-items: start;
}

/* Sidebar */
.sidebar {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
  position: sticky;
  top: var(--spacing-lg);
}

/* Upload Area */
.upload-section {
  background: var(--bg-panel);
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  text-align: center;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-md);
}

.upload-section:hover {
  border-color: var(--accent-primary);
  background: rgba(99, 102, 241, 0.05);
}

.upload-icon {
  color: var(--text-secondary);
  transition: color 0.2s;
}

.upload-section:hover .upload-icon {
  color: var(--accent-primary);
}

.upload-section p {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

.upload-section strong {
  color: var(--text-primary);
  display: block;
  margin-bottom: 4px;
}

.upload-section input {
  display: none;
}

/* Controls */
.controls-section {
  background: var(--bg-panel);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  border: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

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

.control-header label {
  font-weight: 500;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.value-badge {
  background: var(--bg-app);
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-family: monospace;
  color: var(--accent-primary);
  font-weight: 600;
}

/* Range Slider */
input[type="range"] {
  width: 100%;
  height: 6px;
  background: var(--bg-app);
  border-radius: 3px;
  outline: none;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  background: var(--accent-primary);
  border-radius: 50%;
  cursor: pointer;
  transition: transform 0.1s;
  border: 2px solid var(--bg-panel);
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.1);
}

/* Buttons */
.actions {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
  margin-top: var(--spacing-sm);
}

.btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: 10px 16px;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.875rem;
  cursor: pointer;
  transition: all 0.2s;
  border: none;
  width: 100%;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

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

.btn-primary:not(:disabled):hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
}

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

.btn-secondary:not(:disabled):hover {
  background: var(--accent-secondary-hover);
}

/* Preview Area */
.preview-area {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.canvas-card {
  background: var(--bg-panel);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  overflow: hidden;
}

.card-header {
  padding: var(--spacing-md) var(--spacing-lg);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: rgba(0, 0, 0, 0.1);
}

.card-header h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
}

.dimensions-badge, .total-badge {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

.canvas-box {
  padding: var(--spacing-lg);
  display: flex;
  justify-content: center;
  align-items: center;
  background-image: 
    linear-gradient(45deg, #252f42 25%, transparent 25%), 
    linear-gradient(-45deg, #252f42 25%, transparent 25%), 
    linear-gradient(45deg, transparent 75%, #252f42 75%), 
    linear-gradient(-45deg, transparent 75%, #252f42 75%);
  background-size: 20px 20px;
  background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
  min-height: 200px;
}

canvas {
  max-width: 100%;
  height: auto;
  image-rendering: pixelated;
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.3);
  border-radius: 4px;
}

/* Palette Grid */
.palette-card {
  background: var(--bg-panel);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  overflow: hidden;
}

.palette-grid {
  padding: var(--spacing-lg);
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: var(--spacing-md);
}

.color-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  background: var(--bg-app);
  padding: var(--spacing-sm);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  transition: transform 0.2s;
}

.color-item:hover {
  transform: translateY(-2px);
  border-color: var(--accent-primary);
}

.color-swatch {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(255, 255, 255, 0.1);
  flex-shrink: 0;
  box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

.color-info {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.color-info .hex {
  font-family: monospace;
  color: var(--text-primary);
  font-size: 0.875rem;
  font-weight: 600;
}

.color-info .count {
  color: var(--text-secondary);
  font-size: 0.75rem;
}

@media (max-width: 900px) {
  .main-content {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static !important;
  }
}