body {
  margin: 0;
  color: #222;
  background: #fff;
  font-family: Arial, "Noto Sans JP", sans-serif;
  line-height: 1.7;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 40px 20px;
}

header,
section,
footer {
  margin-bottom: 32px;
}

h1 {
  margin: 0 0 8px;
  font-size: 32px;
}

h2 {
  margin: 0 0 12px;
  font-size: 20px;
  border-bottom: 1px solid #ddd;
}

p {
  margin: 0;
}

img,
video {
  display: block;
  max-width: 100%;
  height: auto;
  margin-top: 12px;
}

video {
  width: 100%;
  max-height: 420px;
  background: #000;
}

.code-block {
  margin-top: 12px;
}

.code-block pre {
  overflow-x: auto;
  padding: 12px;
  margin: 0 0 8px;
  border: 1px solid #ddd;
  background: #f7f7f7;
}

.code-block code {
  font-family: Consolas, "Courier New", monospace;
}

table {
  width: 100%;
  margin-top: 12px;
  border-collapse: collapse;
}

th,
td {
  padding: 8px;
  border: 1px solid #ddd;
  text-align: left;
}

th {
  background: #f7f7f7;
}

a {
  color: #0645ad;
}

.item-list {
  padding: 0;
  margin: 0;
  list-style: none;
  border-top: 1px solid #ddd;
}

.item-list li {
  border-bottom: 1px solid #ddd;
}

.item-list a {
  display: block;
  padding: 12px 0;
  color: inherit;
  text-decoration: none;
}

.item-list strong,
.item-list span {
  display: block;
}

.item-list span {
  color: #666;
}

.item-list a:hover strong {
  text-decoration: underline;
}

.download {
  display: inline-block;
  padding: 6px 12px;
  border: 1px solid #999;
  color: #222;
  background: #f7f7f7;
  font: inherit;
  text-decoration: none;
  cursor: pointer;
}

.download:hover {
  background: #eee;
}

footer {
  color: #666;
}

.modal {
  position: fixed;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 20px;
  background: rgba(0, 0, 0, 0.35);
}

.modal[hidden] {
  display: none;
}

.modal-box {
  width: min(680px, 100%);
  padding: 20px;
  border: 1px solid #999;
  background: #fff;
}

.modal-box iframe {
  width: 100%;
  height: 300px;
  border: 1px solid #ddd;
}

.modal-actions {
  display: flex;
  gap: 8px;
  justify-content: flex-end;
  margin-top: 12px;
}

.modal-actions button {
  padding: 6px 12px;
}