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

:root {
  --primary-color: #3f51b5;
  --secondary-color: #f50057;
  --background-color: #f5f5f5;
  --sidebar-width: 280px;
  --code-panel-width: 350px;
  --header-height: 60px;
  --status-height: 30px;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: var(--background-color);
  overflow: hidden;
  height: 100vh;
}

.app-container { display: flex; flex-direction: column; height: 100vh; }

/* header */
.app-header {
  background: linear-gradient(135deg, var(--primary-color), #5c6bc0);
  color: white;
  padding: 0 20px;
  height: var(--header-height);
  display: flex;
  justify-content: space-between;
  align-items: center;
  box-shadow: 0 2px 10px rgba(0,0,0,0.2);
  z-index: 100;
}
.app-header h1 {
  font-size: 1.5rem;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 10px;
}
.header-actions { display: flex; gap: 10px; }
.header-actions button,
.header-actions a {
  background: rgba(255,255,255,0.1);
  border: 1px solid rgba(255,255,255,0.3);
  color: white;
  padding: 8px 16px;
  border-radius: 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 5px;
  transition: all 0.2s;
  text-decoration: none;
}
.header-actions button:hover,
.header-actions a:hover {
  background: rgba(255,255,255,0.2);
  transform: translateY(-1px);
}

.main-content { display: flex; flex: 1; overflow: hidden; }

/* sidebar */
.sidebar {
  width: var(--sidebar-width);
  background: white;
  border-right: 1px solid #ddd;
  padding: 20px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.tool-category h3 {
  color: var(--primary-color);
  margin-bottom: 10px;
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  gap: 8px;
}
.tool-buttons {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-bottom: 20px;
}
.tool-btn {
  padding: 10px;
  border: 1px solid #ddd;
  background: white;
  border-radius: 4px;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 5px;
  transition: all 0.2s;
  font-size: 0.8rem;
}
.tool-btn:hover { border-color: var(--primary-color); background: #f0f4ff; }
.tool-btn.active { background: var(--primary-color); color: white; border-color: var(--primary-color); }

.property-panel { display: flex; flex-direction: column; gap: 12px; }
.property-group { display: flex; flex-direction: column; gap: 5px; }
.property-group label { font-size: 0.8rem; color: #666; }
.property-group select,
.property-group input[type="range"],
.property-group input[type="color"],
.property-group input[type="number"] {
  padding: 5px;
  border: 1px solid #ddd;
  border-radius: 4px;
  width: 100%;
}
.inline-fields {
  display: flex;
  gap: 6px;
}
.inline-fields input {
  flex: 1;
  min-width: 0;
}
#labelOffsetX,
#labelOffsetY {
  max-width: none;
  width: 100%;
}
.property-group .btn-secondary {
  width: 100%;
  padding: 8px;
  font-size: 0.85rem;
}

/* canvas */
.canvas-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding: 20px;
  background: #f8f9fa;
  position: relative;
}
.canvas-container {
  flex: 1;
  border: 1px solid #ddd;
  background: white;
  position: relative;
  overflow: hidden;
  border-radius: 8px;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

/* 关键：不要把 canvas 光标写死成 crosshair，让 JS 能切换 grab/crosshair */
#feynmanCanvas { width: 100%; height: 100%; cursor: inherit; }

.canvas-grid {
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background-image:
    linear-gradient(#e0e0e0 1px, transparent 1px),
    linear-gradient(90deg, #e0e0e0 1px, transparent 1px);
  background-size: 20px 20px;
  pointer-events: none;
  opacity: 0.3;
  z-index: 5;
}

.canvas-controls {
  position: absolute;
  bottom: 30px;
  right: 30px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  background: white;
  padding: 10px;
  border-radius: 8px;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}
.canvas-controls button {
  width: 40px;
  height: 40px;
  border: 1px solid #ddd;
  background: white;
  border-radius: 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}
.canvas-controls button:hover { background: #f5f5f5; border-color: var(--primary-color); }
.canvas-controls button.active { background: var(--primary-color); color: white; border-color: var(--primary-color); }

/* code panel */
.code-panel {
  width: var(--code-panel-width);
  background: white;
  border-left: 1px solid #ddd;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.panel-header {
  padding: 15px 20px;
  border-bottom: 1px solid #ddd;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #f8f9fa;
}
.panel-header h3 {
  color: var(--primary-color);
  font-size: 1rem;
  display: flex;
  align-items: center;
  gap: 8px;
}
.panel-actions { display: flex; gap: 8px; }
.panel-actions button {
  background: white;
  border: 1px solid #ddd;
  width: 32px;
  height: 32px;
  border-radius: 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}
.code-container {
  flex: 1;
  padding: 0;
  overflow: hidden;
  background: #1e1e1e;
  color: #d4d4d4;
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 0.9rem;
  line-height: 1.4;
}

/* TikZ editor textarea */
#tikzEditor{
  width: 100%;
  height: 100%;
  border: none;
  outline: none;
  resize: none;
  background: transparent;
  color: #d4d4d4;
  font-family: 'Consolas','Monaco', monospace;
  font-size: 0.9rem;
  line-height: 1.4;
  padding: 20px;
  white-space: pre;
}

.code-actions {
  padding: 15px 20px;
  border-top: 1px solid #ddd;
  display: flex;
  gap: 10px;
}
.btn-primary, .btn-secondary {
  flex: 1;
  padding: 10px;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: all 0.2s;
}
.btn-primary { background: var(--primary-color); color: white; }
.btn-secondary { background: #6c757d; color: white; }
.btn-primary:hover { background: #303f9f; }
.btn-secondary:hover { background: #5a6268; }

.history-panel {
  border-top: 1px solid #ddd;
  padding: 15px 20px;
  max-height: 200px;
  overflow-y: auto;
}
.history-panel h3 {
  color: var(--primary-color);
  font-size: 0.9rem;
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.history-list { display: flex; flex-direction: column; gap: 5px; }

/* history item (你原 CSS 没有这个类，我补上使其可见可点) */
.history-item{
  padding: 8px 10px;
  background: #f8f9fa;
  border: 1px solid #ddd;
  border-radius: 4px;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.2s;
}
.history-item:hover{
  background: #e9ecef;
  border-color: var(--primary-color);
}

/* status */
.status-bar {
  height: var(--status-height);
  background: white;
  border-top: 1px solid #ddd;
  padding: 0 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: #666;
}
.status-info { display: flex; gap: 20px; }

/* modal */
.modal {
  display: none;
  position: fixed;
  top: 0; left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.5);
  z-index: 1000;
  align-items: center;
  justify-content: center;
}
.modal.active { display: flex; }
.modal-content {
  background: white;
  width: 600px;
  max-width: 90%;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}
.modal-header {
  padding: 20px;
  background: var(--primary-color);
  color: white;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.modal-header .close-btn {
  background: none;
  border: none;
  color: white;
  font-size: 1.5rem;
  cursor: pointer;
  line-height: 1;
}
.modal-body { padding: 20px; }
#exportedCode {
  width: 100%;
  height: 300px;
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 4px;
  font-family: 'Consolas', monospace;
  font-size: 0.9rem;
  resize: vertical;
  margin-bottom: 20px;
}
.modal-actions { display: flex; gap: 10px; justify-content: flex-end; }

/* responsive */
@media (max-width: 1200px) {
  .sidebar { width: 240px; }
  .code-panel { width: 300px; }
}
@media (max-width: 768px) {
  .main-content { flex-direction: column; }
  .sidebar, .code-panel { width: 100%; max-height: 200px; }
  .canvas-controls { bottom: 10px; right: 10px; }
}

/* scrollbars */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: #f1f1f1; border-radius: 4px; }
::-webkit-scrollbar-thumb { background: #c1c1c1; border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: #a8a8a8; }

/* ---------- KaTeX label overlay ---------- */
.label-layer{
  position:absolute;
  left:0; top:0; right:0; bottom:0;
  pointer-events:none;
  z-index: 20;
}

.latex-label{
  position:absolute;
  pointer-events:auto;
  cursor: move;
  user-select: none;
  transform: translate(-50%, -50%);
  color:#000;
  background: transparent;
  padding: 2px 4px;
  border-radius: 4px;
}
.latex-label.dragging{
  outline: 1px dashed rgba(63,81,181,0.8);
  background: rgba(63,81,181,0.06);
}
.latex-label.selected{
  outline: 2px solid rgba(63,81,181,0.8);
  background: rgba(63,81,181,0.06);
}
.latex-label .katex { font-size: 1.1em; }

/* Hand/Space-hand：禁用标签交互，避免挡住拖动画布 */
.label-layer.labels-disabled .latex-label{
  pointer-events: none !important;
}

/* 移动端：让手势交给我们处理（避免浏览器默认滚动/双指缩放） */
.canvas-container,
#feynmanCanvas,
.label-layer {
  touch-action: none;
}

/* 兜底：防止 iOS Safari 在 canvas 上触发页面滚动回弹 */
html, body {
  overscroll-behavior: none;
}