:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --border: #e3e8ef;
  --text: #1f2933;
  --muted: #6b7280;
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-soft: #eef2ff;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.06), 0 8px 24px rgba(0, 0, 0, 0.05);
  --radius: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
}

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

/* Header */
.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 16px 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

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

.logo {
  width: 46px;
  height: 46px;
  border-radius: 12px;
  background: linear-gradient(135deg, #6366f1, #8b5cf6);
  color: #fff;
  font-size: 24px;
  font-weight: 700;
  display: grid;
  place-items: center;
  box-shadow: 0 6px 16px rgba(99, 102, 241, 0.35);
}

.brand-text h1 { margin: 0; font-size: 20px; }
.brand-text p { margin: 2px 0 0; font-size: 13px; color: var(--muted); }

.tabs {
  display: flex;
  gap: 6px;
  background: var(--bg);
  padding: 5px;
  border-radius: 10px;
}

.tab {
  border: none;
  background: transparent;
  padding: 9px 18px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  color: var(--muted);
  cursor: pointer;
  transition: all 0.15s;
}
.tab:hover { color: var(--text); }
.tab.active {
  background: var(--surface);
  color: var(--primary);
  box-shadow: var(--shadow);
}

/* Main */
main { flex: 1; padding: 22px 28px; }

.panel { display: none; height: 100%; flex-direction: column; }
.panel.active { display: flex; }

/* Toolbar */
.toolbar {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.spacer { flex: 1; }

.btn {
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  padding: 9px 16px;
  border-radius: 9px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s;
}
.btn:hover { border-color: #c7cdd6; background: #fafbfc; }
.btn.ghost { background: transparent; }
.btn.primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}
.btn.primary:hover { background: var(--primary-hover); border-color: var(--primary-hover); }

.checkbox {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: var(--muted);
  cursor: pointer;
}
.filename { font-size: 13px; color: var(--muted); }

/* Split layout */
.split {
  flex: 1;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
  min-height: 0;
}

.editor-wrap, .preview-wrap {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  min-height: 460px;
}

.pane-title {
  padding: 10px 16px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
  background: #fafbfc;
  border-bottom: 1px solid var(--border);
}

textarea {
  flex: 1;
  border: none;
  outline: none;
  resize: none;
  padding: 18px;
  font-family: "SFMono-Regular", "JetBrains Mono", Consolas, monospace;
  font-size: 14px;
  line-height: 1.7;
  color: var(--text);
}

.preview {
  flex: 1;
  padding: 22px 26px;
  overflow: auto;
}

/* Drop zone */
.drop-zone {
  border: 2px dashed #cbd2dc;
  border-radius: var(--radius);
  background: var(--surface);
  padding: 50px 20px;
  text-align: center;
  color: var(--muted);
  transition: all 0.2s;
  cursor: pointer;
}
.drop-zone.dragover {
  border-color: var(--primary);
  background: var(--primary-soft);
}
.drop-icon { font-size: 48px; }
.drop-inner p { margin: 14px 0 6px; font-size: 15px; }
.drop-inner small { font-size: 12px; }

/* Markdown body styles (preview & word look) */
.markdown-body { line-height: 1.75; font-size: 15px; color: #24292f; }
.markdown-body h1, .markdown-body h2, .markdown-body h3,
.markdown-body h4, .markdown-body h5, .markdown-body h6 {
  margin: 1.4em 0 0.6em; font-weight: 700; line-height: 1.3;
}
.markdown-body h1 { font-size: 1.9em; border-bottom: 1px solid var(--border); padding-bottom: .3em; }
.markdown-body h2 { font-size: 1.5em; border-bottom: 1px solid var(--border); padding-bottom: .3em; }
.markdown-body h3 { font-size: 1.25em; }
.markdown-body p { margin: 0.8em 0; }
.markdown-body a { color: var(--primary); }
.markdown-body code {
  background: #f1f3f5; padding: 0.15em 0.4em; border-radius: 5px;
  font-family: Consolas, monospace; font-size: 0.9em;
}
.markdown-body pre {
  background: #0f172a; color: #e2e8f0; padding: 16px; border-radius: 10px;
  overflow: auto;
}
.markdown-body pre code { background: transparent; color: inherit; padding: 0; }
.markdown-body blockquote {
  margin: 1em 0; padding: 0.4em 1em; color: var(--muted);
  border-left: 4px solid #d0d7de; background: #f8fafc;
}
.markdown-body table { border-collapse: collapse; width: 100%; margin: 1em 0; }
.markdown-body th, .markdown-body td { border: 1px solid #d0d7de; padding: 8px 12px; }
.markdown-body th { background: #f6f8fa; }
.markdown-body img { max-width: 100%; }
.markdown-body ul, .markdown-body ol { padding-left: 1.6em; }
.markdown-body hr { border: none; border-top: 1px solid var(--border); margin: 1.6em 0; }

/* Toast */
.toast {
  position: fixed;
  bottom: 28px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: #1f2933;
  color: #fff;
  padding: 12px 22px;
  border-radius: 10px;
  font-size: 14px;
  opacity: 0;
  pointer-events: none;
  transition: all 0.25s;
  z-index: 100;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
.toast.error { background: #dc2626; }
.toast.success { background: #16a34a; }

/* Footer */
.site-footer {
  text-align: center;
  padding: 16px;
  font-size: 13px;
  color: var(--muted);
  border-top: 1px solid var(--border);
}

@media (max-width: 820px) {
  .split { grid-template-columns: 1fr; }
  .editor-wrap, .preview-wrap { min-height: 320px; }
  .site-header { flex-direction: column; align-items: flex-start; }
}