:root {
  --bg: #f6f8fb;
  --card: #ffffff;
  --border: #e6e9ef;
  --text: #1f2937;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-soft: #eff4ff;
  --shadow: 0 1px 3px rgba(16,24,40,.06), 0 8px 24px rgba(16,24,40,.05);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* 顶部栏 */
.topbar {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 24px;
  background: var(--card);
  border-bottom: 1px solid var(--border);
}
.topbar h1 { font-size: 18px; margin: 0; font-weight: 600; }
.back { color: var(--muted); text-decoration: none; font-size: 14px; white-space: nowrap; }
.back:hover { color: var(--accent); }

/* 布局 */
.layout {
  flex: 1;
  min-height: 0;
  margin: 0 auto;
  padding: 28px 40px 48px;
  display: grid;
  grid-template-columns: minmax(280px, 0.9fr) minmax(0, 2.1fr);
  grid-template-rows: minmax(0, 1fr);
  gap: 28px;
}
.panel {
  display: flex;
  flex-direction: column;
  gap: 20px;
  min-height: 0;
  position: sticky;
  top: 0;
  align-self: start;
  max-height: 100vh;
  overflow-y: auto;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px;
  box-shadow: var(--shadow);
}
.card h2 { margin: 0 0 16px; font-size: 16px; }
.card-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 16px; }
.card-head h2 { margin: 0; }

/* 表单行 */
.row { display: flex; align-items: center; gap: 12px; margin-bottom: 14px; }
.row label { min-width: 64px; color: var(--muted); font-size: 13px; flex-shrink: 0; }
.row select {
  flex: 1; min-width: 0; padding: 7px 9px;
  border: 1px solid var(--border); border-radius: 8px; font-size: 14px; background: #fff;
}
.hint { color: var(--muted); font-size: 12px; margin: 4px 0 0; line-height: 1.5; }

/* 分段控件 */
.seg { display: inline-flex; border: 1px solid var(--border); border-radius: 8px; overflow: hidden; }
.seg-btn {
  border: none; background: #fff; color: var(--muted);
  padding: 7px 16px; font-size: 13px; cursor: pointer;
}
.seg-btn.on { background: var(--accent); color: #fff; }

/* 按钮 */
.btn {
  border: 1px solid var(--border); background: #fff; color: var(--text);
  padding: 8px 16px; border-radius: 9px; font-size: 14px; cursor: pointer;
  transition: border-color .15s, color .15s, background .15s;
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: #1d4ed8; color: #fff; }
.actions { display: flex; gap: 10px; margin-top: 14px; }

/* 示例下拉菜单 */
.dropdown { position: relative; }
.dropdown-menu {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  z-index: 20;
  display: none;
  min-width: 140px;
  padding: 6px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.12);
}
.dropdown-menu.open { display: block; }
.dropdown-item {
  display: block;
  width: 100%;
  text-align: left;
  border: none;
  background: #fff;
  color: var(--text);
  padding: 8px 10px;
  border-radius: 7px;
  font-size: 13px;
  cursor: pointer;
}
.dropdown-item:hover { background: var(--accent-soft); color: var(--accent); }

/* 编辑框 */
.editor {
  width: 100%;
  min-height: 240px;
  resize: vertical;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 13px;
  line-height: 1.6;
  color: var(--text);
  background: #fbfcfe;
  tab-size: 2;
}
.editor:focus { outline: 2px solid var(--accent-soft); border-color: var(--accent); }
#output { background: #fbfcfe; color: #0f172a; flex: 1; min-height: 240px; }

/* 输入卡片与文本框随栏高拉伸 */
.panel > .card:last-child { display: flex; flex-direction: column; min-height: 0; }
#input { flex: 1; min-height: 200px; }

/* 状态 */
.status { margin-top: 12px; font-size: 13px; min-height: 20px; }
.status.ok { color: #16a34a; }
.status.err { color: #dc2626; }

/* 输出区（预览）撑满栏高 */
.output-pane { display: flex; flex-direction: column; min-height: 0; }
.output-pane > .card { flex: 1; display: flex; flex-direction: column; min-height: 0; }

/* 树视图 */
.tree {
  flex: 1;
  min-height: 240px;
  overflow-x: hidden;
  overflow-y: auto;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px 16px;
  background: #fbfcfe;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 13px;
  line-height: 1.7;
  overflow-wrap: anywhere;
  word-break: break-word;
}
.tree-empty { color: var(--muted); padding: 8px 2px; }
.tree-node { position: relative; }
.tree-row {
  display: flex;
  align-items: flex-start;
  gap: 6px;
  padding: 1px 0;
  cursor: default;
}
.tree-label {
  min-width: 0;
  flex: 1 1 auto;
  overflow-wrap: anywhere;
  word-break: break-word;
}
.tree-row:hover { background: var(--accent-soft); border-radius: 6px; }
.tree-toggle {
  cursor: pointer;
  color: var(--muted);
  width: 14px;
  flex-shrink: 0;
  user-select: none;
  text-align: center;
}
.tree-children { margin-left: 12px; border-left: 1px dashed var(--border); padding-left: 8px; }
.tree-key { color: var(--accent); }
.tree-tag { color: #7c3aed; font-weight: 600; }
.tree-attr { color: #b45309; }
.tree-punc { color: var(--muted); }
.tree-bracket { color: var(--muted); }
.tree-count { color: var(--muted); font-style: italic; }
.tree-value.string { color: #16a34a; }
.tree-value.number { color: #d97706; }
.tree-value.boolean, .tree-value.null { color: #dc2626; }
.tree-text { color: #334155; }
.tree-comment { color: #94a3b8; font-style: italic; }

@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }
  .output-pane { order: 2; }
}