README.css

<style>
  /*
  Obtained from https://github.com/sindresorhus/github-markdown-css/blob/main/github-markdown.css

  Modified a bit to cut out the bloat.
  */
  @media (prefers-color-scheme: dark) {
    body {
      color-scheme: dark;
      --fg-default: #c9d1d9;
      --fg-muted: #8b949e;
      --fg-subtle: #484f58;
      --canvas-default: #0d1117;
      --canvas-subtle: #161b22;
      --border-default: #30363d;
      --border-muted: #21262d;
      --neutral-muted: rgba(110,118,129,0.4);
      --accent-fg: #58a6ff;
      --accent-emphasis: #1f6feb;
      --attention-subtle: rgba(187,128,9,0.15);
    }
  }

  @media (prefers-color-scheme: light) {
    body {
      color-scheme: light;
      --fg-default: #24292f;
      --fg-muted: #57606a;
      --fg-subtle: #6e7781;
      --canvas-default: #ffffff;
      --canvas-subtle: #f6f8fa;
      --border-default: #d0d7de;
      --border-muted: hsla(210,18%,87%,1);
      --neutral-muted: rgba(175,184,193,0.2);
      --accent-fg: #0969da;
      --accent-emphasis: #0969da;
      --attention-subtle: #fff8c5;
    }
  }
  body {
    -ms-text-size-adjust: 100%;
    -webkit-text-size-adjust: 100%;
    color: var(--fg-default);
    background-color: var(--canvas-default);
    font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji";
    font-size: 16px;
    line-height: 1.5;
    word-wrap: break-word;
  }
  body md,
  body figcaption,
  body figure {
    display: block;
  }
  body summary {
    display: list-item;
  }
  body [hidden] {
    display: none !important;
  }
  body a {
    background-color: transparent;
    color: var(--accent-fg);
    text-decoration: none;
  }
  body a:active,
  body a:hover {
    outline-width: 0;
  }
  body abbr[title] {
    border-bottom: none;
    text-decoration: underline dotted;
  }
  body b,
  body strong {
    font-weight: 600;
  }
  body dfn {
    font-style: italic;
  }
  body h1 {
    margin: .67em 0;
    font-weight: 600;
    padding-bottom: .3em;
    font-size: 2em;
    border-bottom: 1px solid var(--border-muted);
  }
  body mark {
    background-color: var(--attention-subtle);
    color: var(--text-primary);
  }
  body small {
    font-size: 90%;
  }
  body sub,
  body sup {
    font-size: 75%;
    line-height: 0;
    position: relative;
    vertical-align: baseline;
  }
  body sub {
    bottom: -0.25em;
  }
  body sup {
    top: -0.5em;
  }
  body img {
    border-style: none;
    max-width: 100%;
    box-sizing: content-box;
    background-color: var(--canvas-default);
  }
  body code,
  body kbd,
  body pre,
  body samp {
    font-family: monospace,monospace;
    font-size: 1em;
  }
  body figure {
    margin: 1em 40px;
  }
  body hr {
    box-sizing: content-box;
    overflow: hidden;
    background: transparent;
    border-bottom: 1px solid var(--border-muted);
    height: .25em;
    padding: 0;
    margin: 24px 0;
    background-color: var(--border-default);
    border: 0;
  }
  body input {
    font: inherit;
    margin: 0;
    overflow: visible;
    font-family: inherit;
    font-size: inherit;
    line-height: inherit;
  }
  body a:hover {
    text-decoration: underline;
  }
  body hr::before {
    display: table;
    content: "";
  }
  body hr::after {
    display: table;
    clear: both;
    content: "";
  }
  body table {
    border-spacing: 0;
    border-collapse: collapse;
    display: block;
    width: max-content;
    max-width: 100%;
    overflow: auto;
  }
  body td,
  body th {
    padding: 0;
  }
  body h1,
  body h2,
  body h3,
  body h4,
  body h5,
  body h6 {
    margin-top: 24px;
    margin-bottom: 16px;
    font-weight: 600;
    line-height: 1.25;
  }
  body h2 {
    font-weight: 600;
    padding-bottom: .3em;
    font-size: 1.5em;
    border-bottom: 1px solid var(--border-muted);
  }
  body h3 {
    font-weight: 600;
    font-size: 1.25em;
  }
  body h4 {
    font-weight: 600;
    font-size: 1em;
  }
  body h5 {
    font-weight: 600;
    font-size: .875em;
  }
  body h6 {
    font-weight: 600;
    font-size: .85em;
    color: var(--fg-muted);
  }
  body p {
    margin-top: 0;
    margin-bottom: 10px;
  }
  body blockquote {
    margin: 0;
    padding: 0 1em;
    color: var(--fg-muted);
    border-left: .25em solid var(--border-default);
  }
  body ul,
  body ol {
    margin-top: 0;
    margin-bottom: 0;
    padding-left: 2em;
  }
  body ol ol,
  body ul ol {
    list-style-type: lower-roman;
  }
  body ul ul ol,
  body ul ol ol,
  body ol ul ol,
  body ol ol ol {
    list-style-type: lower-alpha;
  }
  body dd {
    margin-left: 0;
  }
  body tt,
  body code {
    font-family: ui-monospace,SFMono-Regular,SF Mono,Menlo,Consolas,Liberation Mono,monospace;
    font-size: 12px;
  }
  body pre {
    margin-top: 0;
    margin-bottom: 0;
    font-family: ui-monospace,SFMono-Regular,SF Mono,Menlo,Consolas,Liberation Mono,monospace;
    font-size: 12px;
    word-wrap: normal;
  }
  body ::placeholder {
    color: var(--fg-subtle);
    opacity: 1;
  }
  body>*:first-child {
    margin-top: 0 !important;
  }
  body>*:last-child {
    /*margin-bottom: 0 !important;*/
  }
  body a:not([href]) {
    color: inherit;
    text-decoration: none;
  }
  body p,
  body blockquote,
  body ul,
  body ol,
  body dl,
  body table,
  body pre,
  body md {
    margin-top: 0;
    margin-bottom: 16px;
  }
  body blockquote>:first-child {
    margin-top: 0;
  }
  body blockquote>:last-child {
    margin-bottom: 0;
  }
  body sup>a::before {
    content: "[";
  }
  body sup>a::after {
    content: "]";
  }
  body h1 tt,
  body h1 code,
  body h2 tt,
  body h2 code,
  body h3 tt,
  body h3 code,
  body h4 tt,
  body h4 code,
  body h5 tt,
  body h5 code,
  body h6 tt,
  body h6 code {
    padding: 0 .2em;
    font-size: inherit;
  }
  body ol[type="1"] {
    list-style-type: decimal;
  }
  body ol[type=a] {
    list-style-type: lower-alpha;
  }
  body ol[type=i] {
    list-style-type: lower-roman;
  }
  body div>ol:not([type]) {
    list-style-type: decimal;
  }
  body ul ul,
  body ul ol,
  body ol ol,
  body ol ul {
    margin-top: 0;
    margin-bottom: 0;
  }
  body li>p {
    margin-top: 16px;
  }
  body li+li {
    margin-top: .25em;
  }
  body dl {
    padding: 0;
  }
  body dl dt {
    padding: 0;
    margin-top: 16px;
    font-size: 1em;
    font-style: italic;
    font-weight: 600;
  }
  body dl dd {
    padding: 0 16px;
    margin-bottom: 16px;
  }
  body table th {
    font-weight: 600;
  }
  body table th,
  body table td {
    padding: 6px 13px;
    border: 1px solid var(--border-default);
  }
  body table tr {
    background-color: var(--canvas-default);
    border-top: 1px solid var(--border-muted);
  }
  body table tr:nth-child(2n) {
    background-color: var(--canvas-subtle);
  }
  body table img {
    background-color: transparent;
  }
  body img[align=right] {
    padding-left: 20px;
  }
  body img[align=left] {
    padding-right: 20px;
  }
  body code,
  body tt {
    padding: .2em .4em;
    margin: 0;
    font-size: 85%;
    background-color: var(--neutral-muted);
    border-radius: 6px;
  }
  body code br,
  body tt br {
    display: none;
  }
  body del code {
    text-decoration: inherit;
  }
  body pre code {
    font-size: 100%;
  }
  body pre>code {
    padding: 0;
    margin: 0;
    word-break: normal;
    white-space: pre;
    background: transparent;
    border: 0;
  }
  body pre {
    padding: 16px;
    overflow: auto;
    font-size: 85%;
    line-height: 1.45;
    background-color: var(--canvas-subtle);
    border-radius: 6px;
  }
  body pre code,
  body pre tt {
    display: inline;
    max-width: auto;
    padding: 0;
    margin: 0;
    overflow: visible;
    line-height: inherit;
    word-wrap: normal;
    background-color: transparent;
    border: 0;
  }
  body ::-webkit-calendar-picker-indicator {
    filter: invert(50%);
  }
  body {
    width: 40em;
    margin: auto;
    margin-bottom: 24ex;
  }
  #TOC {
    position: fixed;
    left: 0px;
    top: 0px;
  }
</style>