:root {
  --bg: #f8fafc;
  --surface: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #dbe3ec;
  --accent: #2563eb;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  background: linear-gradient(180deg, #ffffff 0%, var(--bg) 100%);
  font-family: "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  height: 64px;
  padding: 0 16px;
  border-bottom: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.brand h1 {
  margin: 0;
  font-size: 18px;
}

.brand p {
  margin: 2px 0 0;
  font-size: 12px;
  color: var(--muted);
}

.actions {
  display: flex;
  gap: 8px;
}

button {
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  padding: 7px 12px;
  font-size: 13px;
  cursor: pointer;
}

button:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.layout {
  min-height: calc(100vh - 64px);
  padding: 12px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.panel {
  min-height: 0;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.panel-title {
  height: 42px;
  border-bottom: 1px solid var(--border);
  padding: 0 12px;
  display: flex;
  align-items: center;
  color: var(--muted);
  font-size: 13px;
}

#editor {
  width: 100%;
  flex: 1;
  border: 0;
  resize: none;
  padding: 14px;
  color: #111827;
  background: #ffffff;
  font-size: 14px;
  line-height: 1.65;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
}

#editor:focus {
  outline: none;
}

#preview {
  flex: 1;
  overflow: auto;
  padding: 18px;
}

.markdown-body {
  background: transparent;
}

@media (max-width: 960px) {
  .topbar {
    height: auto;
    padding: 10px 12px;
    align-items: flex-start;
    flex-direction: column;
  }

  .layout {
    min-height: auto;
    grid-template-columns: 1fr;
  }

  .panel {
    min-height: 45vh;
  }
}