.menubox {
    border: 1px solid #aaa;
    border-radius: 4px;
    padding: .5em .5em 0;
    background-color:#000033;
    color: white;
    /* border: solid 1px;
    margin-top: 2px;
    margin-left: 10px;
    padding: 10px;
    position: relative;
    background-color:#000033;
    border-radius: 0.5em; */
  }
  hr {
    border-style: none;
    border-top: 1px solid black;
  }
  a.black_color {
    color : black;
    display: block;
    }
  a.white_color {
    color : white;
    display: block;
    }
  .sectionbox {
    border: none;
    margin-top: 2px;
    margin-left: 10px;
    padding: 20px;
    position: relative;
  }
/* https://developer.mozilla.org/ja/docs/Web/HTML/Element/details */ 
details {
    border: 1px solid #aaa;
    border-radius: 4px;
    padding: .5em .5em 0;
    background-color:#000033;
    color: white;
}
summary {
    font-weight: bold;
    margin: -.5em -.5em 0;
    padding: .5em;
}
details[open] {
    padding: .5em;
}
details[open] summary {
    border-bottom: 1px solid #aaa;
    margin-bottom: .5em;
}
details > hr.divide {
  height: 0.5px;
}