div#left_menu {
  position: fixed;
  margin-top: 120px;
  z-index: 100;
  border: 1px solid silver;
}

div#left_menu div#menu_button {
  position: absolute;
  top: -1px;
  right: -21px;
  width: 20px;
  height: 180px;
  cursor: pointer;
  writing-mode: vertical-rl;
  /* 세로로 글자를 출력 */
  text-orientation: upright;
  /* 글자가 직립되도록 설정 */
  border-top: 1px solid silver;
  border-right: 1px solid silver;
  border-bottom: 1px solid silver;
  border-radius: 0px 5px 5px 0px;
  background-color: #e8e9ea;
}

div#left_menu div.accordion {
  display: none;
  width: 20px;
}

div#left_menu div.accordion div.main {
  height: 50px;
  padding-top: 15px;
  padding-left: 10px;
  background-color: white;
  border-bottom: 1px solid silver;
}

div#left_menu div.accordion div.accordion-item {
  height: 50px;
  padding-top: 15px;
  background-color: #eeeeee;
  border-bottom: 1px solid silver;
}

div#left_menu div.accordion div.accordion-item:hover {
  background-color: silver;
}

div#left_menu div.accordion div.accordion-item a {
  padding-left: 20px;
}

div#left_menu div.accordion div.accordion-collapse a {
  padding-left: 30px;
}