/* Modern UI Design for Invoice Generator */
:root {
  color-scheme: light dark;
  
  /* Light theme colors */
  --color-primary: #3b82f6;
  --color-primary-hover: #2563eb;
  --color-primary-light: #dbeafe;
  --color-secondary: #6b7280;
  --color-secondary-hover: #4b5563;
  --color-success: #10b981;
  --color-success-light: #d1fae5;
  --color-danger: #ef4444;
  --color-danger-light: #fee2e2;
  --color-warning: #f59e0b;
  
  --color-background: #ffffff;
  --color-surface: #f9fafb;
  --color-surface-hover: #f3f4f6;
  --color-border: #e5e7eb;
  --color-border-light: #f3f4f6;
  --color-text: #111827;
  --color-text-secondary: #6b7280;
  --color-text-muted: #9ca3af;
  
  /* Typography */
  --font-family: system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  
  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-base: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
  
  /* Border radius */
  --radius-sm: 0.375rem;
  --radius-base: 0.5rem;
  --radius-md: 0.625rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
}

/* Dark theme */
@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #3b82f6;
    --color-primary-hover: #60a5fa;
    --color-primary-light: #1e3a8a;
    --color-secondary: #9ca3af;
    --color-secondary-hover: #d1d5db;
    --color-success: #10b981;
    --color-success-light: #064e3b;
    --color-danger: #ef4444;
    --color-danger-light: #7f1d1d;
    
    --color-background: #111827;
    --color-surface: #1f2937;
    --color-surface-hover: #374151;
    --color-border: #374151;
    --color-border-light: #4b5563;
    --color-text: #f9fafb;
    --color-text-secondary: #d1d5db;
    --color-text-muted: #9ca3af;
  }
}

/* Base styles */
* {
  box-sizing: border-box;
}

body {
  font-family: var(--font-family);
  margin: 0;
  padding: 0;
  background-color: var(--color-surface);
  color: var(--color-text);
  line-height: 1.5;
}

/* Container */
.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: var(--space-6);
}

/* Header */
.header-section {
  margin-bottom: var(--space-8);
}

.header-content {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-6);
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-hover) 100%);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  color: white;
}

.header-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 4rem;
  height: 4rem;
  background: rgba(255, 255, 255, 0.2);
  border-radius: var(--radius-lg);
  backdrop-filter: blur(10px);
}

.header-content h1 {
  margin: 0;
  font-size: var(--font-size-3xl);
  font-weight: 700;
  letter-spacing: -0.025em;
}

.header-content .subtitle {
  margin: var(--space-2) 0 0 0;
  font-size: var(--font-size-lg);
  opacity: 0.9;
  font-weight: 400;
}

/* Main content layout */
.main-content {
  display: grid;
  grid-template-columns: 1fr 400px;
  gap: var(--space-8);
  align-items: start;
}

@media (max-width: 1200px) {
  .main-content {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }
}

/* Form section */
.form-section {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

/* Cards */
.card {
  background: var(--color-background);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-base);
  overflow: hidden;
  transition: all 0.2s ease;
}

.card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary-light);
}

.card-header {
  padding: var(--space-6);
  border-bottom: 1px solid var(--color-border-light);
  background: var(--color-surface);
}

.card-title {
  margin: 0;
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.card-title svg {
  color: var(--color-primary);
  flex-shrink: 0;
}

.card-content {
  padding: var(--space-6);
}

/* Grid layout */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-8);
}

@media (max-width: 768px) {
  .grid {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }
}

/* Input groups */
.input-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.group-title {
  margin: 0 0 var(--space-2) 0;
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--color-text);
  padding-bottom: var(--space-2);
  border-bottom: 2px solid var(--color-primary-light);
}

/* Form fields */
.form-field {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.form-field label {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-1);
}

.form-field input,
.form-field textarea {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-base);
  background: var(--color-background);
  color: var(--color-text);
  font-size: var(--font-size-base);
  transition: all 0.2s ease;
}

.form-field input:focus,
.form-field textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
}

.form-field input:hover,
.form-field textarea:hover {
  border-color: var(--color-primary);
}

/* Items table */
.items-container {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.items-table {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-base);
  overflow: hidden;
}

.items-head {
  display: grid;
  grid-template-columns: 2fr 0.7fr 1fr 1fr 40px;
  gap: var(--space-2);
  align-items: center;
  padding: var(--space-4);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  font-weight: 600;
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.item-row {
  display: grid;
  grid-template-columns: 2fr 0.7fr 1fr 1fr 40px;
  gap: var(--space-2);
  align-items: center;
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-border-light);
  transition: background-color 0.2s ease;
}

.item-row:hover {
  background: var(--color-surface);
}

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

.item-row input {
  width: 100%;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-background);
  color: var(--color-text);
  font-size: var(--font-size-sm);
  transition: all 0.2s ease;
}

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

.item-row .remove {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border: none;
  background: var(--color-danger-light);
  color: var(--color-danger);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s ease;
}

.item-row .remove:hover {
  background: var(--color-danger);
  color: white;
  transform: scale(1.05);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-base);
  background: var(--color-background);
  color: var(--color-text);
  font-size: var(--font-size-base);
  font-weight: 500;
  text-decoration: none;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
  overflow: hidden;
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-hover) 100%);
  border-color: var(--color-primary);
  color: white;
}

.btn-primary:hover {
  box-shadow: var(--shadow-lg);
}

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

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

.btn-add {
  background: linear-gradient(135deg, var(--color-success) 0%, #059669 100%);
  border-color: var(--color-success);
  color: white;
  align-self: flex-start;
}

.btn-add:hover {
  box-shadow: var(--shadow-lg);
}

/* Totals section */
.totals-section {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: var(--space-6);
  flex-wrap: wrap;
}

@media (max-width: 768px) {
  .totals-section {
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-4);
  }
}

.totals-summary {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  min-width: 250px;
}

.total-line {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-3) 0;
  font-size: var(--font-size-base);
}

.total-line:not(:last-child) {
  border-bottom: 1px solid var(--color-border-light);
}

.grand-total {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-primary);
  padding: var(--space-4) 0 !important;
  border-bottom: 2px solid var(--color-primary) !important;
  background: var(--color-primary-light);
  border-radius: var(--radius-base);
  padding: var(--space-4);
  margin-top: var(--space-2);
}

.actions {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
}

@media (max-width: 768px) {
  .actions {
    justify-content: stretch;
  }
  
  .actions .btn {
    flex: 1;
  }
}

/* Preview section */
.preview-section {
  position: sticky;
  top: var(--space-6);
  height: fit-content;
}

.preview-card {
  height: 100%;
}

.preview-container {
  height: 600px;
  border-radius: var(--radius-base);
  overflow: hidden;
  background: var(--color-surface);
}

.preview-container iframe {
  width: 100%;
  height: 100%;
  border: none;
  border-radius: var(--radius-base);
}

/* Responsive adjustments */
@media (max-width: 768px) {
  .container {
    padding: var(--space-4);
  }
  
  .header-content {
    flex-direction: column;
    text-align: center;
    padding: var(--space-4);
  }
  
  .header-content h1 {
    font-size: var(--font-size-2xl);
  }
  
  .card-content,
  .card-header {
    padding: var(--space-4);
  }
  
  .items-head,
  .item-row {
    grid-template-columns: 1.5fr 0.5fr 0.8fr 0.8fr 32px;
    gap: var(--space-1);
    font-size: var(--font-size-xs);
  }
  
  .preview-container {
    height: 400px;
  }
}

@media (max-width: 480px) {
  .items-head,
  .item-row {
    grid-template-columns: 1fr;
    gap: var(--space-2);
  }
  
  .items-head {
    display: none;
  }
  
  .item-row {
    display: flex;
    flex-direction: column;
    padding: var(--space-4);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-base);
    margin-bottom: var(--space-2);
  }
  
  .item-row .remove {
    align-self: flex-end;
  }
}

/* Print styles */
@media print {
  .form-section,
  .header-section {
    display: none !important;
  }
  
  .main-content {
    grid-template-columns: 1fr;
  }
  
  .preview-section {
    position: static;
  }
}

/* Loading states and animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.card {
  animation: fadeIn 0.3s ease-out;
}

/* Focus styles for accessibility */
.btn:focus-visible,
.form-field input:focus-visible,
.form-field textarea:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --color-border: #000000;
    --color-text: #000000;
    --color-background: #ffffff;
  }
  
  .card {
    border: 2px solid var(--color-border);
  }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}