:root {
  --primary: #1976d2;
  --primary: #1976d2;
  --primary: #1976d2;
  --flex-dispay: flex;
}
body {
  margin: 0;
  font-family: system-ui;
  display: var(--flex-dispay);
  height: 100vh;
  #sidebar {
    width: 300px;
    border-right: 1px solid #eee;
    overflow: auto;
  }
}
#content {
  flex: 1;
}
.file-tree ul {
  list-style: none;
  padding-left: 20px;
}
.file-item {
  padding: 8px;
  cursor: pointer;
}
.file-item:hover {
  background: #f5f5f5;
}
.file-item.active {
  color: var(--primary);
  font-weight: bold;
}
iframe {
  width: 100%;
  height: 100%;
  border: none;
}
.header {
  padding: 16px;
  border-bottom: 1px solid #eee;
  font-weight: bold;
}