/* Optimized CSS */
:root {
  --primary-gradient: linear-gradient(135deg, #6a11cb 0%, #2575fc 100%);
  --dark-gradient: linear-gradient(135deg, #3a0ca3 0%, #4361ee 100%);
  --shadow-light: 0 4px 20px rgba(0, 0, 0, 0.08);
  --shadow-hover: 0 10px 25px rgba(0, 0, 0, 0.12);
  --transition: all 0.3s ease;
}

/* Base Styles */
body {
  font-family: 'Sarabun', sans-serif;
  background-color: #f0f2f5;
  transition: background-color 0.3s ease, color 0.3s ease;
  min-height: 100vh;
  margin: 0;
}

/* --- MOVED FROM JS TO CSS FOR PERFORMANCE --- */
.file-item { 
  transition: transform 0.2s, box-shadow 0.2s; 
  cursor: grab; 
  user-select: none; 
  touch-action: none; 
  background: #fff; 
  margin-bottom: 5px; 
  border: 1px solid #dee2e6; 
  border-radius: 4px; 
}
.file-item.dragging { 
  opacity: 0.5; 
  background: #e9ecef; 
  border: 2px dashed #0d6efd; 
}
.file-item.over { 
  border-top: 2px solid #0d6efd; 
}
.file-thumb { 
  width: 40px; 
  height: 40px; 
  object-fit: cover; 
  border-radius: 4px; 
  background: #eee; 
}
.preview-container { 
  max-height: 500px; 
  overflow-y: auto; 
  border: 1px solid #dee2e6; 
  border-radius: 4px; 
  padding: 10px; 
  background: #f8f9fa; 
}
.preview-image { 
  max-width: 100%; 
  height: auto; 
  display: block; 
  margin: 0 auto; 
  box-shadow: 0 2px 5px rgba(0,0,0,0.1); 
}
.preview-pdf { 
  width: 100%; 
  height: 500px; 
  border: none; 
}
.dark-mode .file-item { 
  background: #2d3238; 
  border-color: #495057; 
  color: #fff; 
}
/* ------------------------------------------- */

/* Layout Optimizations */
.container { will-change: transform; }

.card {
  border-radius: 1rem;
  transition: var(--transition);
  box-shadow: var(--shadow-light);
  overflow: hidden;
  will-change: transform;
}
.card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-hover);
}
.card-header {
  border-top-left-radius: 1rem;
  border-top-right-radius: 1rem;
  background: var(--primary-gradient);
  color: white;
  font-weight: 600;
}

/* Drop Zone */
#drop-zone {
  cursor: pointer;
  transition: var(--transition), transform 0.2s ease;
  border-style: dashed !important;
  background-color: #f8f9fa;
  position: relative;
  overflow: hidden;
  contain: layout style paint;
}
#drop-zone::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
  transition: 0.5s;
}
#drop-zone:hover::before { left: 100%; }
#drop-zone.dragover {
  background-color: #e9ecef;
  border-color: #0d6efd !important;
  transform: scale(1.02);
}

/* Buttons */
.btn {
  transition: var(--transition);
  font-weight: 500;
  position: relative;
  overflow: hidden;
  z-index: 1;
  border: none;
  contain: layout style;
}
.btn::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(255,255,255,0.1);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform 0.3s ease;
  z-index: -1;
}
.btn:hover::after {
  transform: scaleX(1);
  transform-origin: left;
}

.btn-custom-grey {
  background-color: #9ea7b0;
  color: white;
  border: none;
  border-radius: 6px;
}
.btn-custom-grey:hover:not(:disabled) {
  background-color: #868e96;
  color: white;
}

.btn-custom-blue {
  background-color: #5a97f2;
  color: white;
  border: none;
  border-radius: 6px;
}
.btn-custom-blue:hover:not(:disabled) {
  background-color: #4a80d4;
  color: white;
}
.btn:disabled {
  opacity: 0.65;
  cursor: not-allowed;
}

/* List Items */
.list-group-item {
  background-color: #fff;
  border: 1px solid #dee2e6;
  margin-bottom: -1px;
  transition: var(--transition);
  contain: layout style;
}
.list-group-item:hover {
  background-color: #f8f9fa;
  transform: translateX(5px);
}

/* Modal */
.modal-content {
  border-radius: 1rem;
  border: none;
  box-shadow: var(--shadow-hover);
}
.modal-header {
  border-bottom: 1px solid #dee2e6;
  background: var(--primary-gradient);
  color: white;
  border-top-left-radius: 1rem;
  border-top-right-radius: 1rem;
}
.modal-title { font-weight: 600; }

/* Animation */
@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-20px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.05); }
  100% { transform: scale(1); }
}
.btn-primary { animation: pulse 2s infinite; }
.btn-primary:hover { animation: none; }

/* Progress Bar */
.progress {
  border-radius: 10px;
  overflow: hidden;
  background-color: #e9ecef;
  contain: layout;
}
.progress-bar {
  transition: width 0.3s ease;
  will-change: width;
}

/* Dark Mode */
body.dark-mode {
  background-color: #121212;
  color: #e0e0e0;
}
body.dark-mode .card {
  background-color: #1e1e1e;
  border-color: #333;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}
body.dark-mode .card-header { background: var(--dark-gradient) !important; }
body.dark-mode .modal-content {
  background-color: #1e1e1e;
  color: #e0e0e0;
}
body.dark-mode .modal-header {
  background: var(--dark-gradient) !important;
  border-bottom-color: #333;
}
body.dark-mode .form-control {
  background-color: #2a2a2a;
  color: #e0e0e0;
  border-color: #555;
}
body.dark-mode .form-control:focus {
  background-color: #333;
  color: #ffffff;
  border-color: #4dabf7;
}

/* Performance Optimizations */
#file-list li,
#result-area .d-flex {
  will-change: transform, opacity;
  contain: layout style;
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .btn-primary { animation: none; }
}

@media (max-width: 768px) {
  .card { border-radius: 0.75rem; margin: 0.5rem; }
  .card-body { padding: 1rem !important; }
  #drop-zone { padding: 1.5rem !important; }
  .modal-dialog { margin: 0.5rem; }
  .btn-lg {
    padding: 0.6rem 0.5rem !important;
    font-size: 0.85rem !important;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }
  .btn i { font-size: 0.9rem; }
}

@media print {
  .btn, #toggle-dark-mode, #drop-zone { display: none !important; }
  .card { box-shadow: none !important; border: 1px solid #000 !important; }
}

body.dark-mode #drop-zone { background-color: #2a2a2a; border-color: #555; color: #ccc; }
body.dark-mode #drop-zone.dragover { background-color: #333; border-color: #4dabf7 !important; }
body.dark-mode .list-group-item { background-color: #2c2c2c; color: #e0e0e0; border-color: #444; }
body.dark-mode .list-group-item:hover { background-color: #383838; color: #ffffff; }
body.dark-mode .form-control, body.dark-mode .form-select { background-color: #2a2a2a; color: #e0e0e0; border-color: #555; }
body.dark-mode .form-control:focus, body.dark-mode .form-select:focus { background-color: #333; color: #ffffff; border-color: #4dabf7; }
body.dark-mode .btn-primary { background-color: #0d6efd; border-color: #0d6efd; }
body.dark-mode .btn-primary:hover { background-color: #1a7eff; border-color: #1a7eff; }
body.dark-mode .btn-secondary { background-color: #3a3a3a; color: #eee; border-color: #555; }
body.dark-mode .btn-outline-secondary { color: #ccc; border-color: #555; }
body.dark-mode .btn-outline-secondary:hover { background-color: #3a3a3a; color: #fff; }
body.dark-mode .text-muted { color: #888 !important; }