/* ==================== Reset & Base ==================== */
* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: #f5f5f7;
  color: #333;
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ==================== Header ==================== */
header { padding: 30px 20px 20px; }
.header-content { display: flex; justify-content: space-between; align-items: flex-start; max-width: 900px; margin: 0 auto; flex-wrap: wrap; gap: 16px; }
.header-text { text-align: left; }
header h1 { font-size: 2rem; color: #1a1a1a; margin-bottom: 8px; }
header p { color: #666; font-size: 1rem; }
.header-actions { display: flex; align-items: center; gap: 12px; }

/* ==================== Language Switch ==================== */
.lang-switch { display: flex; gap: 4px; background: #e5e5e7; padding: 4px; border-radius: 20px; }
.lang-btn { padding: 6px 14px; border: none; background: transparent; border-radius: 16px; font-size: 0.85rem; font-weight: 500; color: #666; cursor: pointer; transition: all 0.2s; }
.lang-btn:hover { color: #333; }
.lang-btn.active { background: #fff; color: #333; box-shadow: 0 1px 3px rgba(0,0,0,0.1); }

/* ==================== Category Nav ==================== */
.category-nav { display: flex; justify-content: center; gap: 8px; padding: 0 20px 16px; flex-wrap: wrap; max-width: 900px; margin: 0 auto; }
.category-btn { display: flex; align-items: center; gap: 8px; padding: 10px 20px; border: none; background: #e5e5e7; border-radius: 20px; font-size: 0.95rem; font-weight: 500; color: #555; cursor: pointer; transition: all 0.2s; }
.category-btn:hover { background: #d5d5d7; }
.category-btn.active { background: #0071e3; color: #fff; }
.category-btn svg { flex-shrink: 0; }

/* ==================== Main Content ==================== */
main { flex: 1; padding: 0 20px 40px; max-width: 900px; margin: 0 auto; width: 100%; }
.category-section { display: none; }
.category-section.active { display: block; }

/* ==================== Tool Nav ==================== */
.tool-nav { display: flex; gap: 6px; padding: 0 0 16px; flex-wrap: nowrap; overflow-x: auto; }
.tab-btn { padding: 8px 16px; border: none; background: #e5e5e7; border-radius: 16px; font-size: 0.85rem; font-weight: 500; color: #555; cursor: pointer; transition: all 0.2s; white-space: nowrap; }
.tab-btn:hover { background: #d5d5d7; }
.tab-btn.active { background: #0071e3; color: #fff; }

/* ==================== Tool Panel ==================== */
.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* ==================== Tool Container ==================== */
.tool-container { background: #fff; border-radius: 16px; padding: 24px; box-shadow: 0 2px 12px rgba(0,0,0,0.08); margin-bottom: 20px; }

/* ==================== Upload Area ==================== */
.upload-area { position: relative; border: 2px dashed #d5d5d7; border-radius: 12px; min-height: 180px; display: flex; align-items: center; justify-content: center; cursor: pointer; transition: border-color 0.2s, background 0.2s; overflow: hidden; }
.upload-area:hover, .upload-area.dragover { border-color: #0071e3; background: rgba(0,113,227,0.03); }
.upload-area input[type="file"].file-input-hidden {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
  z-index: 5;
}

.upload-placeholder { text-align: center; color: #888; }
.upload-placeholder svg { margin-bottom: 12px; color: #ccc; }
.upload-placeholder p { font-size: 1rem; margin-bottom: 4px; }
.upload-placeholder span { font-size: 0.85rem; color: #aaa; }

.preview-area { position: relative; padding: 16px; width: 100%; }
.preview-area.hidden { display: none; }
.preview-area img, .preview-area video, .preview-area audio { max-width: 100%; max-height: 250px; display: block; margin: 0 auto; border-radius: 8px; }
.preview-area audio { width: 100%; border-radius: 8px; }

.clear-btn { position: absolute; top: 8px; right: 8px; width: 28px; height: 28px; border: none; background: rgba(0,0,0,0.6); color: #fff; border-radius: 50%; font-size: 1.2rem; line-height: 1; cursor: pointer; display: flex; align-items: center; justify-content: center; }
.clear-btn:hover { background: rgba(0,0,0,0.8); }

/* ==================== Controls ==================== */
.controls { margin-top: 20px; }
.control-group { margin-bottom: 16px; }
.control-group > label { display: block; font-size: 0.9rem; font-weight: 500; color: #555; margin-bottom: 8px; }

.format-buttons { display: flex; gap: 8px; }
.format-btn { flex: 1; padding: 10px 16px; border: 2px solid #e5e5e7; background: #fff; border-radius: 8px; font-size: 0.9rem; font-weight: 600; color: #555; cursor: pointer; transition: all 0.2s; }
.format-btn:hover { border-color: #0071e3; color: #0071e3; }
.format-btn.active { border-color: #0071e3; background: #0071e3; color: #fff; }

input[type="range"] { width: 100%; height: 6px; border-radius: 3px; background: #e5e5e7; appearance: none; outline: none; }
input[type="range"]::-webkit-slider-thumb { appearance: none; width: 20px; height: 20px; border-radius: 50%; background: #0071e3; cursor: pointer; }

.preset-buttons { display: flex; flex-wrap: wrap; gap: 8px; }
.preset-btn, .rotate-preset-btn, .wm-pos-btn, .collage-layout-btn, .vc-quality-btn, .thumb-size-btn { padding: 8px 14px; border: 1px solid #e5e5e7; background: #fff; border-radius: 6px; font-size: 0.85rem; color: #555; cursor: pointer; transition: all 0.2s; }
.preset-btn:hover, .rotate-preset-btn:hover, .wm-pos-btn:hover, .collage-layout-btn:hover, .vc-quality-btn:hover, .thumb-size-btn:hover { border-color: #0071e3; color: #0071e3; }
.preset-btn.active, .rotate-preset-btn.active, .wm-pos-btn.active, .collage-layout-btn.active, .vc-quality-btn.active, .thumb-size-btn.active { border-color: #0071e3; background: #e5f0ff; color: #0071e3; }

.size-inputs { display: flex; align-items: center; gap: 12px; }
.size-inputs input { flex: 1; padding: 10px 12px; border: 1px solid #e5e5e7; border-radius: 8px; font-size: 0.95rem; outline: none; transition: border-color 0.2s; }
.size-inputs input:focus { border-color: #0071e3; }
.size-inputs span { color: #888; font-weight: 500; }

input[type="checkbox"] { width: 18px; height: 18px; accent-color: #0071e3; cursor: pointer; }

.text-input { width: 100%; padding: 10px 12px; border: 1px solid #e5e5e7; border-radius: 8px; font-size: 0.95rem; outline: none; transition: border-color 0.2s; }
.text-input:focus { border-color: #0071e3; }

.flip-buttons { display: flex; gap: 8px; }
.flip-btn { flex: 1; padding: 8px 14px; border: 1px solid #e5e5e7; background: #fff; border-radius: 6px; font-size: 0.85rem; color: #555; cursor: pointer; transition: all 0.2s; }
.flip-btn:hover { border-color: #0071e3; color: #0071e3; }
.flip-btn.active { border-color: #0071e3; background: #e5f0ff; color: #0071e3; }

/* ==================== Buttons ==================== */
.action-btn { width: 100%; padding: 14px; border: none; background: #0071e3; color: #fff; border-radius: 10px; font-size: 1rem; font-weight: 600; cursor: pointer; transition: background 0.2s; margin-top: 8px; }
.action-btn:hover { background: #0077ed; }
.action-btn.secondary { background: #34c759; margin-top: 8px; }
.action-btn.secondary:hover { background: #2db14e; }

/* ==================== Result Area ==================== */
.result-area { margin-top: 20px; padding: 16px; background: #f5f5f7; border-radius: 10px; text-align: center; }
.result-area.hidden { display: none; }
.result-area audio { width: 100%; margin-bottom: 12px; border-radius: 8px; }
.result-info { margin-bottom: 12px; font-size: 0.9rem; color: #666; display: flex; justify-content: center; gap: 16px; flex-wrap: wrap; }

.download-btn { display: inline-block; padding: 12px 32px; background: #34c759; color: #fff; text-decoration: none; border-radius: 8px; font-weight: 600; transition: background 0.2s; }
.download-btn:hover { background: #2db14e; }

/* ==================== Collage Thumbnails ==================== */
#img-collage-thumbnails, #audio-merge-list { display: flex; flex-wrap: wrap; gap: 8px; padding: 8px; justify-content: center; }
.collage-thumb { position: relative; width: 60px; height: 60px; border-radius: 6px; overflow: hidden; }
.collage-thumb img { width: 100%; height: 100%; object-fit: cover; }
.remove-thumb { position: absolute; top: 2px; right: 2px; width: 18px; height: 18px; background: rgba(0,0,0,0.6); color: #fff; border-radius: 50%; font-size: 12px; line-height: 18px; text-align: center; cursor: pointer; }
.merge-item { padding: 6px 12px; background: #e5f0ff; border-radius: 6px; font-size: 0.85rem; color: #0071e3; }

/* ==================== Waveform Canvas ==================== */
#audio-waveform-canvas, #audio-waveform-result-canvas { width: 100%; height: 100px; background: #fafafa; border-radius: 8px; display: block; margin: 0 auto; }
#audio-waveform-result-canvas { height: 200px; }

/* ==================== Video Thumbnail Canvas ==================== */
#video-thumb-canvas { max-width: 100%; border-radius: 8px; display: block; margin: 0 auto 12px; }

/* ==================== Footer ==================== */
footer { text-align: center; padding: 20px; color: #888; font-size: 0.85rem; }

/* ==================== Utility ==================== */
.hidden { display: none !important; }

/* ==================== Responsive ==================== */
@media (max-width: 480px) {
  header h1 { font-size: 1.6rem; }
  .tool-container { padding: 16px; }
  .category-nav { gap: 6px; }
  .category-btn { padding: 8px 14px; font-size: 0.85rem; }
  .tab-btn { padding: 7px 12px; font-size: 0.8rem; }
  .format-buttons { flex-wrap: wrap; }
  .format-btn { font-size: 0.85rem; padding: 8px 12px; }
  .preset-buttons { gap: 6px; }
  .preset-btn, .rotate-preset-btn { padding: 6px 10px; font-size: 0.8rem; }
  header { padding: 20px 16px 16px; }
  main { padding: 0 16px 30px; }
}