summary {
  position: relative;
  display: block; /* 矢印を消す */
  padding: 10px;
  padding-left: 25px;
  cursor: pointer;
  background-color: #f1f5ff;
  transition: 0.2s;
}
summary:hover {
  background-color: #c1d3ff;
}
summary::-webkit-details-marker {
  display: none;
}
/* 疑似要素でアイコンを表示 */
summary::before,
summary::after {
  content: "";
  margin: auto;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
}
summary::before {
  width: 20px;
  height: 20px;
  border-radius: 50em;
  background-color: #113285;
}
summary::after {
  left: 8px;
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 4px 0 4px 8px;
  border-color: transparent transparent transparent #fff;
  box-sizing: border-box;
  transition: .1s;
}

/* オープン時 */
details[open] summary {
  background-color: #c1d3ff;
  max-height:9999px;
}
details[open] summary::after {
  transform: rotate(90deg);
  left: 6px;
  top: 2px;
  max-height:9999px;
}

/* アニメーション */
details[open] .wrapper {
  animation: accordionOpen 0.5s ease;
}
@keyframes accordionOpen {
  0% {
    opacity: 0;
    transform: translateY(-5px);
  }
  100% {
    opacity: 1;
    transform: none;
  }
}