.content {
  width: 100%;
}

/* 3段の間隔 */
.content > div:first-child {
  margin-bottom: 5px;
}

.content > img {
  display: block;
  width: 100%;
  height: auto;
  margin-bottom: 5px;
}

/* 解説 */
.content details {
  width: 100%;
  margin: 0;
}

.content summary {
  width: 100%;
  padding: 8px 12px;
  background: #999;
  color: #fff;
  cursor: pointer;
  list-style: none;
}

.content summary::-webkit-details-marker {
  display: none;
}

/* 開閉マーク */
.content summary::after {
  content: "＋";
  float: right;
}

.content details[open] summary::after {
  content: "−";
}

/* 解説ボックス */
.description {
  width: 100%;
  padding: 12px;
  background: #eaeaea;
  line-height: 1.7;
}