:root {
  --bg: #f3f5f8;
  --panel: #ffffff;
  --panel-soft: #f8fafc;
  --text: #172033;
  --muted: #687385;
  --border: #dfe5ee;
  --accent: #3b82f6;
  --accent-dark: #1d4ed8;
  --shadow: 0 20px 60px rgba(15, 23, 42, 0.08);
  --code-bg: #0f172a;
  --code-text: #e2e8f0;
}

body.dark {
  --bg: #0b1020;
  --panel: #121a2d;
  --panel-soft: #182238;
  --text: #e5e7eb;
  --muted: #9ca3af;
  --border: #2b3650;
  --accent: #60a5fa;
  --accent-dark: #3b82f6;
  --shadow: 0 20px 60px rgba(0, 0, 0, 0.35);
  --code-bg: #020617;
  --code-text: #e5e7eb;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
  background: radial-gradient(circle at top left, rgba(59, 130, 246, 0.16), transparent 32%), var(--bg);
  color: var(--text);
}

.app {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 340px 1fr;
  transition: grid-template-columns 0.2s ease;
}

.app.sidebar-collapsed {
  grid-template-columns: 0 1fr;
}

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  padding: 26px;
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: blur(20px);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  scrollbar-width: none;
  -ms-overflow-style: none;
  transition: transform 0.2s ease, opacity 0.2s ease;
}

.sidebar::-webkit-scrollbar {
  display: none;
}

.app.sidebar-collapsed .sidebar {
  transform: translateX(-100%);
  opacity: 0;
  pointer-events: none;
  border-right: 0;
  padding: 0;
  overflow: hidden;
}

body.dark .sidebar {
  background: rgba(18, 26, 45, 0.72);
}

.brand {
  display: flex;
  gap: 14px;
  align-items: center;
  margin-bottom: 28px;
}

.logo {
  width: 52px;
  height: 52px;
  border-radius: 16px;
  display: grid;
  place-items: center;
  background: linear-gradient(135deg, var(--accent), #8b5cf6);
  color: white;
  font-weight: 800;
  letter-spacing: -0.03em;
}

.brand h1 {
  margin: 0 0 4px;
  font-size: 18px;
}

.brand p {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
}

.upload-card {
  display: grid;
  gap: 8px;
  justify-items: center;
  padding: 30px 18px;
  border: 1.5px dashed var(--border);
  border-radius: 22px;
  background: var(--panel);
  cursor: pointer;
  transition: 0.2s ease;
}

.upload-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.upload-card input {
  display: none;
}

.upload-icon {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: var(--panel-soft);
  color: var(--accent);
  font-size: 28px;
}

.upload-card small,
.file-info span {
  color: var(--muted);
}

.file-info {
  margin: 18px 0;
  padding: 16px;
  border-radius: 16px;
  background: var(--panel-soft);
  border: 1px solid var(--border);
  display: grid;
  gap: 6px;
}

.actions {
  display: grid;
  gap: 10px;
  margin-bottom: 22px;
}

button {
  border: 0;
  border-radius: 14px;
  padding: 12px 14px;
  background: var(--text);
  color: var(--panel);
  cursor: pointer;
  font-weight: 650;
  transition: 0.18s ease;
}

button:hover:not(:disabled) {
  transform: translateY(-1px);
  opacity: 0.92;
}

button:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

#downloadBtn {
  background: var(--accent);
  color: white;
}

#clearBtn {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}

.toc-panel {
  padding: 18px;
  border-radius: 18px;
  background: var(--panel);
  border: 1px solid var(--border);
}

.toc-panel h2 {
  margin: 0 0 12px;
  font-size: 15px;
}

#toc {
  display: grid;
  gap: 8px;
  color: var(--muted);
  font-size: 14px;
}

#toc a {
  color: var(--muted);
  text-decoration: none;
  line-height: 1.4;
}

#toc a:hover {
  color: var(--accent);
}

.toc-h2 { padding-left: 12px; }
.toc-h3 { padding-left: 24px; }
.toc-h4 { padding-left: 36px; }

.workspace {
  padding: 26px 36px 36px;
  overflow: hidden;
}

.workspace-toolbar {
  max-width: 980px;
  margin: 0 auto 16px;
  display: flex;
  justify-content: flex-end;
}

#sidebarToggleBtn {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
  padding: 9px 12px;
  border-radius: 12px;
}

.markdown-body {
  max-width: 980px;
  margin: 0 auto;
  padding: 46px;
  border-radius: 28px;
  background: var(--panel);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  line-height: 1.85;
  font-size: 16px;
}

.markdown-body.empty {
  color: var(--muted);
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4 {
  color: var(--text);
  line-height: 1.25;
  letter-spacing: -0.03em;
  scroll-margin-top: 30px;
}

.markdown-body h1 { font-size: 38px; margin-top: 0; }
.markdown-body h2 { font-size: 28px; margin-top: 42px; padding-bottom: 8px; border-bottom: 1px solid var(--border); }
.markdown-body h3 { font-size: 22px; margin-top: 30px; }
.markdown-body h4 { font-size: 18px; margin-top: 24px; }

.markdown-body p,
.markdown-body li {
  color: var(--text);
}

.markdown-body a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid rgba(59, 130, 246, 0.35);
}

.markdown-body blockquote {
  margin: 22px 0;
  padding: 16px 20px;
  border-left: 4px solid var(--accent);
  border-radius: 12px;
  background: var(--panel-soft);
  color: var(--muted);
}

.markdown-body code {
  padding: 3px 6px;
  border-radius: 7px;
  background: var(--panel-soft);
  color: var(--accent-dark);
  font-family: "SFMono-Regular", Consolas, monospace;
}

.markdown-body pre {
  overflow-x: auto;
  padding: 20px;
  border-radius: 18px;
  background: var(--code-bg);
}

.markdown-body pre code {
  padding: 0;
  background: transparent;
  color: var(--code-text);
}

.markdown-body img {
  max-width: 100%;
  border-radius: 18px;
  display: block;
  margin: 22px auto;
}

.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  overflow: hidden;
  margin: 24px 0;
  border-radius: 14px;
  display: block;
  overflow-x: auto;
}

.markdown-body th,
.markdown-body td {
  padding: 12px 14px;
  border: 1px solid var(--border);
}

.markdown-body th {
  background: var(--panel-soft);
}

@media (max-width: 860px) {
  .app {
    grid-template-columns: 1fr;
  }

  .app.sidebar-collapsed {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: relative;
    height: auto;
    transform: none;
    opacity: 1;
    pointer-events: auto;
  }

  .workspace {
    padding: 18px;
  }

  .markdown-body {
    padding: 26px;
    border-radius: 22px;
  }
}