html {
  scroll-behavior: smooth; /* スムーススクロール */
}

section {
  scroll-margin-top: 50px; /* スクロール位置をsectionの上に数値分空ける */
  height: 500px;
  padding: 60px 20px;
}
section:nth-child(even) {
  background-color: #eee;
}

/* 以下はただの装飾 */
header {
  background-color: #73c7ce;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
}

nav ul {
  display: flex;
  justify-content: center;
}

nav ul li a {
  color: #fff;
  display: flex;
  align-items: center;
  height: 50px;
  text-decoration: none;
  padding: 0 20px;
  transition: 0.2s;
}

nav ul li a:hover {
  background-color: #fff;
  color: #73c7ce;
}

.wrap {
  padding-top: 50px;
}

#btn_pagetop {
  background-color: transparent;
  border-radius: 50%;
  color: #fff;
  display: flex;
  justify-content: center;
  align-items: center;
  text-decoration: none;
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 100px;
  height: 100px;
  transition: .3s;
}

#btn_pagetop::before,
#btn_pagetop::after {
  content: "";
  border-radius: 50%;
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
}

#btn_pagetop::before {
  background: #73c7ce;
  z-index: -1;
  transition: .3s;
}

#btn_pagetop::after {
  border: 3px solid #73c7ce;
  box-sizing: border-box;
}

#btn_pagetop:hover {
  background-color: #fff;
  color: #73c7ce;
}

#btn_pagetop:hover::before {
  transform: scale(0);
  opacity: 0;
}

//アンカー時のハッシュタグを消す
window.onhashchange = () => {
  if (window.location.hash) {
    window.history.replaceState(
      null,
      "",
      window.location.pathname + window.location.search
    );
  }
};