:root {
  --primary: #3a86ff;
  --primary-dark: #1a56c5;
  --primary-light: #60a5fa;
  --success: #22c55e;
  --success-dark: #16a34a;
  --danger: #ef4444;
  --danger-dark: #dc2626;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;
  --text-dark: #374151;
  --text-light: #f3f4f6;
  --bg-light: #ffffff;
  --bg-dark: #1f2937;
  
  --font-sans: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --border-radius: 0.5rem;
  --transition-normal: 0.2s ease-in-out;
}

.light-theme {
  --text: var(--text-dark);
  --bg-primary: var(--bg-light);
  --bg-secondary: var(--gray-100);
  --border-color: var(--gray-200);
}

.dark-theme {
  --text: var(--text-light);
  --bg-primary: var(--bg-dark);
  --bg-secondary: var(--gray-700);
  --border-color: var(--gray-600);
}

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

body {
  font-family: var(--font-sans);
  line-height: 1.5;
  color: var(--text);
  background-color: var(--bg-primary);
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

body.light-theme {
  color: var(--text-dark);
  background-color: var(--bg-light);
}

body.dark-theme {
  color: var(--text-light);
  background-color: var(--bg-dark);
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem 1rem;
}

/* Header */
header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
}

h1 {
  font-size: 1.875rem;
  font-weight: 700;
  color: var(--primary);
}

.theme-toggle {
  background-color: var(--bg-secondary);
  border: none;
  border-radius: 9999px;
  padding: 0.5rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color var(--transition-normal);
}

.theme-toggle:hover {
  background-color: var(--gray-200);
}

.dark-theme .theme-toggle:hover {
  background-color: var(--gray-600);
}

.theme-toggle svg {
  width: 1.5rem;
  height: 1.5rem;
  stroke: currentColor;
  stroke-width: 2;
  fill: none;
}

.sun-icon {
  display: none;
  color: #f59e0b;
}

.moon-icon {
  display: block;
  color: var(--gray-700);
}

.dark-theme .sun-icon {
  display: block;
}

.dark-theme .moon-icon {
  display: none;
}

/* Main container */
.editor-container {
  background-color: var(--bg-primary);
  border-radius: var(--border-radius);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  padding: 1.5rem;
  transition: background-color var(--transition-normal);
}

/* Image preview */
.image-preview-container {
  margin-bottom: 2rem;
}

.image-preview-container h2 {
  margin-bottom: 0.5rem;
}

/* Controls (nút Clear) - Styles cũ bị ghi đè/tái sử dụng bên dưới */
.controls {
  display: flex;
  justify-content: flex-end;
  margin-bottom: 0.5rem;
}

.drop-area {
  border: 2px dashed var(--border-color);
  border-radius: var(--border-radius);
  height: 5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 0.5rem;
  background-color: var(--bg-secondary);
  cursor: pointer;
  transition: all var(--transition-normal);
}

.drop-area:hover, .drop-area.dragover {
  background-color: var(--gray-200);
  border-color: var(--primary);
}

.dark-theme .drop-area:hover, .dark-theme .drop-area.dragover {
  background-color: var(--gray-600);
}

.drop-message {
  text-align: center;
}

.drop-message svg {
  width: 2rem;
  height: 2rem;
  stroke: var(--gray-400);
  stroke-width: 2;
  fill: none;
  margin: 0 auto;
}

.drop-message p {
  margin-top: 0.25rem;
  font-size: 0.875rem;
  color: var(--gray-500);
}

.file-info {
  font-size: 0.875rem;
  color: var(--gray-500);
  margin-bottom: 1rem;
}

.preview-area {
  min-height: 200px;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 0.5rem;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  overflow: hidden;
  transition: background-color var(--transition-normal);
}

.preview-images {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}

.preview-item {
  position: relative;
  max-width: 150px;
  max-height: 150px;
  cursor: move;
}

.preview-item img {
  max-width: 150px;
  max-height: 150px;
  object-fit: contain;
  border: 1px solid var(--border-color);
  border-radius: 0.25rem;
}

.preview-item.dragging {
  opacity: 0.5;
}

.delete-btn {
  position: absolute;
  top: -0.5rem;
  right: -0.5rem;
  width: 1.5rem;
  height: 1.5rem;
  background-color: var(--danger);
  color: white;
  border: none;
  border-radius: 50%;
  font-size: 1rem;
  line-height: 1.5rem;
  text-align: center;
  cursor: pointer;
  transition: background-color var(--transition-normal);
}

.delete-btn:hover {
  background-color: var(--danger-dark);
}

.no-image-message {
  text-align: center;
}

.no-image-message svg {
  width: 3rem;
  height: 3rem;
  stroke: var(--gray-400);
  stroke-width: 2;
  fill: none;
  margin: 0 auto;
}

.no-image-message p {
  margin-top: 0.5rem;
  font-size: 0.875rem;
  color: var(--gray-500);
}

/* Control panel */
.control-panel {
  margin-bottom: 2rem;
}

.control-panel h2 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--primary);
  margin-bottom: 1rem;
}

.option-box {
  margin-bottom: 1rem;
  background-color: var(--bg-secondary);
  border-radius: var(--border-radius);
  padding: 1rem;
  transition: background-color var(--transition-normal);
}

.option-header {
  display: flex;
  align-items: center;
  margin-bottom: 0.5rem;
}

.option-header input[type="checkbox"] {
  margin-right: 0.5rem;
}

.option-header label {
  font-weight: 500;
}

.option-content {
  margin-top: 0.75rem;
}

.input-group {
  margin-bottom: 0.75rem;
}

.input-group label {
  display: block;
  font-size: 0.875rem;
  margin-bottom: 0.25rem;
}

.input-group input[type="number"],
.input-group select {
  width: 100%;
  padding: 0.5rem;
  border: 1px solid var(--border-color);
  border-radius: 0.25rem;
  background-color: var(--bg-primary);
  color: var(--text);
  transition: all var(--transition-normal);
}

.input-group input[type="color"] {
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  border: none;
  border-radius: 0.25rem;
  cursor: pointer;
}

.range-container {
  display: flex;
  align-items: center;
  margin-top: 0.5rem;
}

.range-label {
  font-size: 0.75rem;
  color: var(--gray-500);
}

input[type="range"] {
  flex: 1;
  margin: 0 0.5rem;
  height: 0.5rem;
  background-color: var(--gray-200);
  border-radius: 9999px;
  appearance: none;
  -webkit-appearance: none;
  cursor: pointer;
}

.dark-theme input[type="range"] {
  background-color: var(--gray-600);
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 1rem;
  height: 1rem;
  border-radius: 50%;
  background: var(--primary);
  cursor: pointer;
}

.note {
  font-size: 0.75rem;
  font-style: italic;
  margin-top: 0.5rem;
  color: var(--gray-500);
}

.upload-btn {
  display: inline-block;
  padding: 0.5rem 0.75rem;
  font-size: 0.875rem;
  background-color: var(--gray-200);
  color: var(--gray-700);
  border-radius: 0.25rem;
  cursor: pointer;
  transition: all var(--transition-normal);
}

.dark-theme .upload-btn {
  background-color: var(--gray-600);
  color: var(--gray-300);
}

.upload-btn:hover {
  background-color: var(--gray-300);
}

.dark-theme .upload-btn:hover {
  background-color: var(--gray-500);
}

/* Process button */
.process-btn {
  margin-top: 1.5rem;
  width: 100%;
}

.process-btn svg {
  width: 1.25rem;
  height: 1.25rem;
  margin-right: 0.5rem;
}

.process-btn.loading svg {
  display: none;
}

.process-btn.loading::after {
  content: "";
  display: inline-block;
  width: 1rem;
  height: 1rem;
  border: 2px solid white;
  border-top-color: transparent;
  border-radius: 50%;
  margin-left: 0.5rem;
  animation: spin 1s linear infinite;
}

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

.status-message {
  text-align: center;
  font-size: 0.875rem;
  margin-top: 0.75rem;
  min-height: 1.2em;
  color: var(--gray-500);
}

/* Result panel */
.result-panel {
  margin-top: 2rem;
}

.result-header {
  display: flex;
  align-items: center;
  margin-bottom: 1rem;
}

.result-header svg {
  width: 1.25rem;
  height: 1.25rem;
  stroke: #22c55e;
  stroke-width: 2;
  fill: none;
  margin-right: 0.5rem;
}

.result-header h2 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--primary);
}

.result-image-area {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 1rem;
  display: flex;
  justify-content: center;
  margin-bottom: 1rem;
  transition: background-color var(--transition-normal);
}

.result-image-area img {
  max-width: 100%;
  max-height: 400px;
}

.result-info {
  background-color: var(--bg-secondary);
  padding: 1rem;
  border-radius: var(--border-radius);
  margin-bottom: 1rem;
  font-size: 0.875rem;
  transition: background-color var(--transition-normal);
}

.compression-info {
  margin-top: 0.25rem;
  font-weight: 500;
  color: #22c55e;
}

.download-btn {
  width: 100%;
  text-decoration: none;
  display: inline-flex;
  justify-content: center;
  align-items: center;
}

.download-btn svg {
  width: 1.25rem;
  height: 1.25rem;
  margin-right: 0.5rem;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.5rem 1rem;
  font-weight: 500;
  border: none;
  border-radius: 0.25rem;
  cursor: pointer;
  transition: all var(--transition-normal);
}

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

.btn-primary:hover {
  background-color: var(--primary-dark);
}

.btn-destructive {
  background-color: var(--danger);
  color: white;
  font-size: 0.875rem;
  padding: 0.375rem 0.75rem;
}

.btn-destructive:hover {
  background-color: var(--danger-dark);
}

.btn-success {
  background-color: var(--success);
  color: white;
  font-weight: 500;
}

.btn-success:hover {
  background-color: var(--success-dark);
}

.btn svg {
  stroke: currentColor;
  stroke-width: 2;
  fill: none;
}

/* Footer */
footer {
  text-align: center;
  margin-top: 2rem;
  font-size: 0.875rem;
  color: var(--gray-500);
}

/* Responsive */
@media (max-width: 640px) {
  .container {
    padding: 1rem;
  }
  
  header {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .theme-toggle {
    margin-top: 1rem;
    align-self: flex-end;
  }
  
  .editor-container {
    padding: 1rem;
  }
}

/* ----------------------------------- */
/* NEW UI UPGRADES */
/* ----------------------------------- */

/* Thêm các biến CSS để làm nổi bật tùy chọn */
:root {
  --highlight-bg: var(--gray-50); 
  --highlight-border: var(--primary);
}

.dark-theme {
  --highlight-bg: var(--gray-800);
}

/* ----------------------------------- */
/* 2. Bố cục Grid cho Editor Container */
/* ----------------------------------- */
/* Đã có padding: 1.5rem trong styles cũ */

.grid-layout {
  display: grid;
  /* Màn hình lớn: 2 cột (3 phần cho ảnh, 2 phần cho controls) */
  grid-template-columns: 3fr 2fr; 
  gap: 2rem;
  margin-bottom: 2rem; /* Tách biệt với Result Panel */
}

/* ----------------------------------- */
/* 3. Cải thiện Khu vực Xem trước (Preview Area) */
/* ----------------------------------- */

.image-preview-container h2 {
  margin-bottom: 1rem;
  color: var(--primary-dark);
}

.preview-area {
  min-height: 250px; /* Tăng chiều cao tối thiểu */
  overflow: auto; 
  align-items: flex-start; 
  padding: 1rem;
  position: relative; /* Dùng cho nút Clear */
}

.preview-area > .no-image-message,
.preview-area > .preview-images {
  /* Căn chỉnh lại nội dung bên trong preview-area đã được đổi kiểu hiển thị */
  width: 100%;
}

.controls {
  position: absolute; /* Đặt nút Xóa lên góc trên bên phải */
  top: 0.5rem;
  right: 0.5rem;
  z-index: 10; 
  display: block; 
}

.preview-images {
  padding-top: 2rem; /* Tạo không gian cho nút Xóa */
  justify-content: flex-start; /* Căn lề trái các ảnh nhỏ */
}

/* ----------------------------------- */
/* 4. Cải thiện Option Box */
/* ----------------------------------- */

.option-box {
  border: 1px solid var(--border-color); 
}

/* Hiệu ứng làm nổi bật khi checkbox được chọn */
.option-box .option-header:has(input:checked) {
  background-color: var(--highlight-bg); /* Làm nổi bật header khi chọn */
  border-left: 5px solid var(--primary); /* Thanh màu nhấn */
  padding-left: 0.5rem;
  margin-left: -1rem; 
  padding-right: 1rem;
  transition: all var(--transition-normal);
}

.option-box .option-header label {
  font-weight: 600; /* Nhấn mạnh tiêu đề tùy chọn */
  cursor: pointer;
}

/* Chắc chắn rằng label có cursor: pointer khi nó liên kết với input (checkbox) */
.option-box .option-header label[for] {
  cursor: pointer;
}

/* ----------------------------------- */
/* 5. Result Panel (Hiển thị nổi bật hơn) */
/* ----------------------------------- */
.result-panel {
  margin-top: 3rem; 
  border-top: 2px solid var(--success); /* Viền nổi bật cho phần kết quả */
  padding-top: 1.5rem;
}

.result-header h2 {
  color: var(--success); 
}

/* ----------------------------------- */
/* 6. Responsive cho Bố cục Grid */
/* ----------------------------------- */

@media (max-width: 900px) {
  /* Chuyển sang bố cục 1 cột trên màn hình nhỏ/tablet */
  .grid-layout {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
  
  /* Cải thiện vị trí của nút xóa trên màn hình nhỏ */
  .preview-area {
    padding-top: 2.5rem; 
  }
  
  .controls {
    top: 0.5rem;
  }
  
  .preview-images {
    padding-top: 0;
  }
}