body {
  padding-bottom: 25vh;
}

a,
a:visited {
  color: #1d7484;
}

header {
  text-align: start;
  font-size: 12px;
  color: #555;
}
header img {
  max-width: 120px;
  margin: 0;
}
header a.to-site:hover {
  border: none;
}
header div.to-repo {
  color: gray;
  text-align: end;
  font-size: 9pt;
  margin-bottom: 1em;
}
header div.to-repo a {
  display: inline;
  text-align: end;
}

h2 {
  margin-top: 80px;
  font-size: 1.75em;
  border-bottom: 2px solid #afafaf;
}

h3 {
  font-size: 1.25em;
  margin-top: 60px;
}

h2 + h3 {
  margin-top: 40px;
}

p {
  text-align: justify;
}

h1 .sub {
  display: block;
  font-size: 0.8em;
}

h1 > a:hover,
div > a:hover {
  border: none;
}

div > a,
div > a + em {
  display: block;
  text-align: center;
}

div > a > img {
  margin-bottom: 0;
  width: 100%;
}

div > a + em {
  font-size: 0.8em;
  color: #555;
  margin-bottom: 2em;
}

.reference-source {
  max-width: 90%;
  margin: auto 0 auto auto;
  font-size: 0.9em;
  line-height: 1.4;
  text-align: justify;
}

.youtube img {
  height: 100%;
  object-fit: cover;
}

.youtube,
.youtubeplay {
  width: 100%;
  aspect-ratio: 16 / 9;
  margin: 10px auto;
  display: inline-block;
  position: relative;
  overflow: hidden;
}

.youtube iframe,
.youtubeplay iframe {
  width: 100%;
  height: 100%;
}

.youtube::before {
  position: absolute;
  content: "Click to Play";
  color: #fff;
  text-align: center;
  font-size: 22px;
  font-weight: bold;
  padding-top: 25%;
  background: rgba(0, 0, 0, 0.6);
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 10;
  transition: all 0.3s;
}

.youtube:hover::before {
  background: rgba(0, 0, 0, 0.7);
  cursor: pointer;
  transition: all 0.3s;
}

footer {
  border-top: 1px solid gray;
  margin-top: 6em;
}
footer .content {
  margin: 0 1em;
}

footer .content h1 {
  text-align: start;
  font-size: 0.9em;
}
footer .content h1::before {
  content: "■";
}
footer .content h2 {
  font-size: 1em;
  border: none;
  margin: 0;
}
footer .content ul {
  font-size: 0.9em;
  line-height: 1.4;
}

footer .content img {
  margin: 10px 0;
  height: 300px;
}

.link-card {
  border: 1px solid #c4c4c4;
  border-radius: 8px;
  font-size: 1rem;
  margin: 2em 0;
  min-height: 120px;
  display: flex;
}
.link-card .preview {
  width: 120px;
}
.link-card .preview a {
  display: contents;
}
.link-card .preview img {
  object-fit: cover;
  width: 100%;
  height: 100%;
  border-radius: 8px 0 0 8px;
}
.link-card .detail {
  padding: 8px 16px;
}
.link-card .detail .title {
  text-align: left;
  font-size: 16px;
  font-weight: bold;
  line-height: 1.1;
  margin-bottom: 0.5em;
}
.link-card .detail .description {
  text-align: left;
  font-size: 12px;
  color: gray;
}