GitHub Pagesのmarkdownに自作テーマを適用し、ダークテーマや、tex数式や、シンタックスハイライトと言語名表示つきのコードブロックを使えるようにする

:root{
  --b1: #181921;
  --b2: #1a2638;
  --b3: #323e52;
  --b4: #323e52;
  --b4: #1a2a2c;
}

body {
  padding:0 0;
  margin: 0 0;
  font:14px/1.5 "OpenSansRegular", "Helvetica Neue", Helvetica, Arial, sans-serif;
  color:#ddd9ca;
  font-weight: normal;
  background: #181921;
  display: flex;
  align-items: center;
  flex-direction: column;
  /* background-attachment: fixed !important; */
}

.linkcard {
  border-radius: 5em;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.linkcard img{
  width: 8em;
  height: 12em;
  object-fit: cover;
  border-radius: 5em 5em 5em 5em   
}
.row {
  display: flex;
  flex-direction: row;
  align-items: center;
}
.row a{
  margin: 1em;
}
.columun {
  display: flex;
  flex-direction: column;
  align-items: center;
}

article{
  background-color: #1a2638;
  margin: 1em 0em;
  padding: 1em;
  border-radius: 1em;
}
article article {
  margin: 1em -0.5em;
  padding: 1em 0.5em;
  background-color: #323e52;
}

.wrapper {
  margin: 0 auto;
  padding: 30px;
  max-width:660px;
  position:relative;
}

svg {
  max-width: 660px;
  max-height: 400px;
}

img{
  max-height: 80vh;
  max-width: 80vw;
}

section img {
  max-width: 100%;
}

button {
  background-color: slategrey;
  color: white;
  border-radius: 1em;
  border-width: 0;
}
button:hover {
  filter: hue-rotate(20deg) saturate(90%) brightness(90%)
}
button.playing {
  filter: hue-rotate(20deg) saturate(200%)
}
.mikuButton button {
  background-color: #47848b;
}
.musicButton button {
  background-color: #8b4755;
}

h1, h2, h3, h4, h5, h6 {
  margin:0px;
  color: white;
  font-family: 'OpenSansRegular', "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-weight: normal;
}

p, ul, ol, table, pre, dl {
  margin:0 0 20px;
}

h1, h2, h3 {
  line-height:1.1;
}

h1 {font-size:28px;}

h2 {font-size: 24px;}

h3 {
  font-size: 18px;
  line-height: 24px;
  font-family: 'OpenSansRegular', "Helvetica Neue", Helvetica, Arial, sans-serif !important;
  font-weight: normal;
}

a {
  color:#f5abb5;
  font-weight:400;
  text-decoration:none;
}
a:hover {
  color: #f69eaa;
  text-decoration: none;
}

a small {
  font-size:11px;
  color:#666;
  margin-top:-0.6em;
  display:block;
}


ul{
  list-style-image:url('../images/bullet.png');
}

strong {
  font-family: 'OpenSansBold', "Helvetica Neue", Helvetica, Arial, sans-serif !important;
  font-weight: normal;
}

blockquote {
  border-left:3px solid cadetblue;
  font-style: italic;
  color: #c8dfdf;
  margin:0;
  padding:0 0 0 20px;
  
}

.codepre:before {
  display: block;
  /* position: absolute; */
  inset-block-start: 0em;
  inset-inline-start: 0;
  /* content: attr(class); */
  padding-block: .5em;
  padding-inline: 1em;
  inline-size: fit-content;
  background-color: var(--b3);
  color: white;
  font-family: Monaco, Bitstream Vera Sans Mono, Lucida Console, Terminal, monospace;
  border-radius: .5em .5em 0 0;
  /* content: "python"; */
}

.code {
  display: block;
  position: relative;
  padding: 1em 1em;
  background-color: var(--b2);
  border-radius: 0 .5em .5em .5em;
  font-family: Monaco, Bitstream Vera Sans Mono, Lucida Console, Terminal, monospace;
  color:#efefef;
  font-size:13px;
  overflow: auto;
  /* overflow-y: hidden; */
}

.mermaidpre {
  /* background-color: #5292c7; */
  display: flex;
  justify-content: center;
}
/* .language-mermaid {
  background-color: #51e1bd;
  margin: 0 auto;
} */

table {
  width:100%;
  border-collapse:collapse;
}

th {
  text-align:left;
  padding:5px 10px;
  border-bottom:1px solid #434343;
  color: #b6b6b6;
  font-family: 'OpenSansSemibold', "Helvetica Neue", Helvetica, Arial, sans-serif !important;
  font-weight: normal;
}

td {
  text-align:left;
  padding:5px 10px;
  border-bottom:1px solid #434343;
}

hr {
  border: 0;
  outline: none;
  height: 3px;
  background: transparent url('../images/hr.gif') center center repeat-x;
  margin: 0 0 20px;
}

dt {
  color:#F0E7D5;
  font-family: 'OpenSansSemibold', "Helvetica Neue", Helvetica, Arial, sans-serif !important;
  font-weight: normal;
}


/* コードブロック */

@media print, screen and (max-width: 720px) {

  #title {
    .credits {
      display: block;
      width: 100%;
      line-height: 30px;
      text-align: center;

      .left {
        float: none;
        display: block;
      }

      .right {
        float: none;
        display: block;
      }
    }
  }
}

@media print, screen and (max-width: 480px) {

  #header {
    margin-top: -20px;
  }

  section {
    margin-top: 40px;
  }
  nav {
    display: none;
  }
}
/*
   generated by rouge http://rouge.jneen.net/
   original base16 by Chris Kempson (https://github.com/chriskempson/base16)
*/

.highlight table td { padding: 5px; }
.highlight table pre { margin: 0; }
.highlight, .highlight .w {
  color: #d0d0d0;
}
.highlight .err {
  color: #151515;
  background-color: #ac4142;
}

.highlight .c, .highlight .cd, .highlight .cm, .highlight .c1, .highlight .cs {
  color: #888;
}
.highlight .cp {
  color: #f4bf75;
}
.highlight .nt {
  color: #f4bf75;
}
.highlight .o, .highlight .ow {
  color: #adcace;
}
.highlight .pi {
  color: #d0d0d0;
}
.highlight .p {
  color: #dbd700;
}
.highlight .gi {
  color: #90a959;
}
.highlight .gd {
  color: #ac4142;
}
.highlight .gh {
  color: #aa759f;
  font-weight: bold;
}
.highlight .k, .highlight .kn, .highlight .kp, .highlight .kr, .highlight .kv {
  color: #5292c7;
}
.highlight .s {
  color: #ea8e85;
}

.highlight .kc {
  color: #d28445;
}
.highlight .kt {
  color: #d28445;
}
.highlight .kd {
  color: #d28445;
}
.highlight .sb, .highlight .sc, .highlight .sd, .highlight .s2, .highlight .sh, .highlight .sx, .highlight .s1 {
  color: #90a959;
}
.highlight .sr {
  color: #75b5aa;
}
.highlight .si {
  color: #8f5536;
}
.highlight .se {
  color: #8f5536;
}
.highlight .nn {
  color: #51e1bd;
}

.highlight .nc {
  color: #f4bf75;
}
.highlight .no {
  color: #f4bf75;
}
.highlight .na {
  color: #6a9fb5;
}
.highlight .nf, .highlight .nb {
  color: #dcdcaa;
}
.highlight .m, .highlight .mf, .highlight .mh, .highlight .mi, .highlight .il, .highlight .mo, .highlight .mb, .highlight .mx {
  color: #ce916a;
}
.highlight .ss {
  color: #90a959;
}

pre:before {
  display: block;
  /* position: absolute; */
  inset-block-start: 0em;
  inset-inline-start: 0;
  /* content: attr(class); */
  padding-block: .5em;
  padding-inline: 1em;
  inline-size: fit-content;
  background-color: #323e52;
  color: white;
  border-radius: .5em .5em 0 0;
  /* content: "python"; */
  
}

code {

  display: block;
  position: relative;
  padding: 1em 1em;
  background-color: #1a2638;
  border-radius: 0 .5em .5em .5em;
  font-family: Monaco, Bitstream Vera Sans Mono, Lucida Console, Terminal, monospace;
  color:#efefef;
  font-size:13px;
  overflow: auto;
  /* overflow-y: hidden; */
}