body {
  overflow-x: hidden;
}
.container h1 {
  display: none !important;
}
.btn-common {
  display: inline-block;
  padding: 8px 20px;
  background-color: #333;
  color: #fff;
  text-decoration: none;
  border-radius: 5px;
  font-size: 13px;
  transition: background-color 0.3s;
  text-align: center;
}
.back-to-toc {
  width: 100%;
  display: flex;
  justify-content: center;
  margin: 40px 0;
}

.back-to-toc .btn-common {
  display: inline-block;
  text-align: center;
}


/* 強制的に中央寄せ */
.back-to-toc {
  text-align: center !important;
  margin: 60px 0;
}