:root {
  --bg: #f6f8fa;
  --panel: #ffffff;
  --border: #d0d7de;
  --text: #1f2328;
  --text-dim: #656d76;
  --accent: #0969da;
  --accent-soft: #ddf4ff;
  --hover: #f3f4f6;
  --dragbar: transparent;
  --dragbar-hover: var(--accent);
  --radius: 8px;
  --topbar-h: 48px;
  --toolbar-h: 40px;
  --statusbar-h: 28px;
}

html[data-theme='dark'] {
  --bg: #0d1117;
  --panel: #161b22;
  --border: #30363d;
  --text: #e6edf3;
  --text-dim: #8b949e;
  --accent: #58a6ff;
  --accent-soft: #1f3a5f;
  --hover: #21262d;
  --dragbar-hover: var(--accent);
}

* { box-sizing: border-box; }

/* 仅对搜索引擎/屏幕阅读器可见的主标题 */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

html, body {
  height: 100%;
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC',
    'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  background: var(--bg);
  color: var(--text);
  transition: background 0.2s, color 0.2s;
}

body {
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ---------- 顶栏 ---------- */
.topbar {
  height: var(--topbar-h);
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 12px;
  background: var(--panel);
  border-bottom: 1px solid var(--border);
}

.topbar-left { display: flex; align-items: center; gap: 16px; }
.topbar-right { display: flex; align-items: center; gap: 12px; }

.logo { font-weight: 700; font-size: 16px; user-select: none; }
.logo span { color: var(--accent); }

.menus { display: flex; gap: 4px; }

.menu { position: relative; }

.menu-btn {
  padding: 6px 10px;
  border: none;
  background: transparent;
  color: var(--text);
  font-size: 13px;
  border-radius: 6px;
  cursor: pointer;
}
.menu-btn:hover, .menu.open .menu-btn { background: var(--hover); }

.menu-dropdown {
  display: none;
  position: absolute;
  top: calc(100% + 4px);
  left: 0;
  min-width: 180px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15);
  padding: 4px;
  z-index: 100;
}
.menu.open .menu-dropdown { display: block; }

.menu-dropdown button {
  display: block;
  width: 100%;
  text-align: left;
  padding: 8px 12px;
  border: none;
  background: transparent;
  color: var(--text);
  font-size: 13px;
  border-radius: 6px;
  cursor: pointer;
}
.menu-dropdown button:hover { background: var(--accent-soft); color: var(--accent); }

.sync-scroll-toggle {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--text-dim);
  cursor: pointer;
  user-select: none;
}

.icon-btn {
  width: 32px;
  height: 32px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  border-radius: 6px;
  cursor: pointer;
  font-size: 14px;
}
.icon-btn:hover { background: var(--hover); }

/* ---------- 工具栏 ---------- */
.toolbar {
  height: var(--toolbar-h);
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 2px;
  padding: 0 8px;
  background: var(--panel);
  border-bottom: 1px solid var(--border);
  overflow-x: auto;
}

.toolbar button {
  min-width: 34px;
  height: 28px;
  padding: 0 6px;
  border: none;
  background: transparent;
  color: var(--text);
  font-size: 13px;
  border-radius: 6px;
  cursor: pointer;
  white-space: nowrap;
}
.toolbar button:hover { background: var(--accent-soft); color: var(--accent); }

.toolbar .sep {
  width: 1px;
  height: 18px;
  background: var(--border);
  margin: 0 6px;
  flex: 0 0 auto;
}

/* 工具栏下拉（标题 H1-H6） */
.toolbar.dropdown-open { overflow: visible; }

.toolbar-dropdown {
  position: relative;
  flex: 0 0 auto;
}

.toolbar-dropbtn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
}
.toolbar-dropbtn .caret {
  font-size: 9px;
  color: var(--text-dim);
  transition: transform 0.15s;
}
.toolbar-dropdown.open .toolbar-dropbtn {
  background: var(--accent-soft);
  color: var(--accent);
}
.toolbar-dropdown.open .caret { transform: rotate(180deg); }

.toolbar-dropdown-menu {
  display: none;
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  min-width: 168px;
  padding: 6px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.18);
  z-index: 200;
}
.toolbar-dropdown.open .toolbar-dropdown-menu { display: block; }

.toolbar-dropdown-menu button {
  display: flex;
  align-items: center;
  gap: 10px;
  width: 100%;
  height: auto;
  min-width: 0;
  padding: 6px 10px;
  border: none;
  background: transparent;
  color: var(--text);
  border-radius: 6px;
  cursor: pointer;
  text-align: left;
}
.toolbar-dropdown-menu button:hover { background: var(--accent-soft); }

.toolbar-dropdown-menu .hd {
  width: 26px;
  font-weight: 700;
  color: var(--text-dim);
  flex: 0 0 auto;
  line-height: 1.4;
}
.toolbar-dropdown-menu .hd1 { font-size: 18px; }
.toolbar-dropdown-menu .hd2 { font-size: 16px; }
.toolbar-dropdown-menu .hd3 { font-size: 15px; }
.toolbar-dropdown-menu .hd4 { font-size: 14px; }
.toolbar-dropdown-menu .hd5 { font-size: 13px; }
.toolbar-dropdown-menu .hd6 { font-size: 12px; }

.toolbar-dropdown-menu .hd-text {
  font-size: 12px;
  color: var(--text-dim);
}

.toolbar-dropdown-menu button.is-active {
  background: var(--accent-soft);
}
.toolbar-dropdown-menu button.is-active .hd,
.toolbar-dropdown-menu button.is-active .hd-text {
  color: var(--accent);
}

/* ---------- 主体 ---------- */
.workspace {
  flex: 1 1 auto;
  display: flex;
  min-height: 0;
}

.pane {
  min-width: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.pane-edit { background: var(--panel); }

.pane-preview {
  background: var(--bg);
  overflow-y: auto;
}

.editor-wrap {
  flex: 1;
  display: flex;
  min-width: 0;
  min-height: 0;
  position: relative;
}

/* 行号栏 */
.gutter {
  flex: 0 0 auto;
  width: 52px;
  padding: 20px 10px 20px 0;
  overflow: hidden;
  text-align: right;
  background: var(--panel);
  color: var(--text-dim);
  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  font-size: 14px;
  user-select: none;
  border-right: 1px solid var(--border);
}

#editor {
  flex: 1;
  width: 100%;
  resize: none;
  border: none;
  outline: none;
  padding: 20px 24px 20px 12px;
  background: var(--panel);
  color: var(--text);
  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  font-size: 14px;
  line-height: 1.7;
  tab-size: 4;
}

/* 隐藏的镜像层：用于测量每行折行后的真实高度 */
.mirror {
  position: absolute;
  top: 0;
  left: -99999px;
  visibility: hidden;
  pointer-events: none;
  white-space: pre-wrap;
  overflow-wrap: break-word;
}

#preview { padding: 20px 32px; }

.dragbar {
  flex: 0 0 6px;
  cursor: col-resize;
  background: var(--dragbar);
  transition: background 0.15s;
}
.dragbar:hover, .dragbar.dragging { background: var(--dragbar-hover); }

/* ---------- 状态栏 ---------- */
.statusbar {
  height: var(--statusbar-h);
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 24px;
  padding: 0 16px;
  background: var(--panel);
  border-top: 1px solid var(--border);
  font-size: 12px;
  color: var(--text-dim);
  user-select: none;
}

#saveStatus.dirty { color: #d29922; }

/* ---------- 预览内代码高亮（暗色适配） ---------- */
html[data-theme='dark'] .markdown-body {
  color-scheme: dark;
}
html[data-theme='dark'] .markdown-body pre,
html[data-theme='dark'] .markdown-body code {
  background: #161b22;
}
html[data-theme='dark'] .markdown-body table tr {
  background-color: transparent;
}
html[data-theme='dark'] .markdown-body table tr:nth-child(2n) {
  background-color: #161b22;
}

/* ---------- 响应式 ---------- */
@media (max-width: 768px) {
  .sync-scroll-toggle { display: none; }
  .workspace { flex-direction: column; }
  .pane { flex: 1 1 50% !important; }
  .dragbar { display: none; }
  #editor, #preview { padding: 12px 16px; }
}