body {
  margin: 0;
  display: flex;
  height: 100vh;
  font-family: sans-serif;
}


/* ヘッダー */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 250px;
  height: 60px;
  background: #2c3e50;
  color: white;
  display: flex;
  align-items: center;
  padding-left: 20px;
  font-size: 20px;
  z-index: 1000;
}



/* 左メニュー */
.sidebar {
  width: 250px;
  background: #2c3e50;
  color: white;
  padding: 10px;
  margin-top: 40px;
}

.menu-item {
  cursor: pointer;
  padding: 10px;
}

.submenu {
  display: none;
  padding-left: 15px;
}

.submenu a {
  display: block;
  padding: 8px;
  color: white;
  text-decoration: none;
}
.submenu.open {
  display: block;
}
.submenu a:hover {
  background: #34495e;
}
.submenu a {
  display: block;
  padding: 8px;
  color: white;
  text-decoration: none;
}

.submenu a:hover {
  background: #34495e;
}

/* これがハイライト */
.submenu a.active {
  background:#1abc9c;
}

/* 右コンテンツ */
.content {
  flex: 1;
}

iframe {
  width: 100%;
  height: 100%;
  border: none;
}