obsidian-gh-styles.css

/* ============================================================ *
  GitHub-style Markdown for Obsidian
  Save as: <vault>/.obsidian/snippets/github-markdown.css
  Enable in: Settings -> Appearance -> CSS snippets
  Works on top of the Default theme (and most others).
 * ============================================================ */
body {
  /* --- Heading scale (the part flat themes drop) --- */
  --h1-size: 2em;
  --h2-size: 1.6em;
  --h3-size: 1.4em;
  --h4-size: 1.25em;
  --h5-size: 1.1em;
  --h6-size: 1em;

  /* --- Horizontal rule (the `---` thematic break) --- */
  --hr-thickness: 4px;

  /* --- top padding above headers --- */
  --p-spacing: 0.25rem;
}

/* Same underline + tighter top spacing in Live Preview (editing) */
.cm-s-obsidian .HyperMD-header-1,
.cm-s-obsidian .HyperMD-header-2 {
  border-bottom: 1px solid var(--background-modifier-border);
}

/* Inline code and code blocks at GitHub's 85% size */
.markdown-rendered code,
.cm-s-obsidian .cm-inline-code {
  font-size: 80%;
}

.theme-dark {
  --code-background: #3e3e3e;
}

.theme-light {
  --code-background: #e9e9e9;
}