/* ハンバーガー */
nav {
    display: block;
    position: fixed;
    top: 0;
    left: -300px;
    bottom: 0;
    width: 300px;
    background: #ffffff;
    overflow-x: hidden;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    transition: all .5s;
    z-index: 3;
    opacity: 0;
  }
  .open nav {
    left: 0;
    opacity: 1;
  }
  nav .inner {
    padding: 25px;
  }
  nav .inner ul {
    list-style: none;
    margin: 0;
    padding: 0;
  }
  nav .inner ul li {
    position: relative;
    margin: 0;
    border-bottom: 1px solid #333;
    line-height:28px;
  }
  nav .inner ul li a {
    display: block;
    color: #333;
    font-size: 14px;
    padding: 1em;
    text-decoration: none;
    transition-duration: 0.2s;
  }
  nav .inner ul li a:hover {
    background: #e4e4e4;
  }
  
  .toggle_btn {
    display: block;
    position: fixed;
    top: 30px;
    right: 30px;
    width: 30px;
    height: 30px;
    transition: all .5s;
    cursor: pointer;
    z-index: 3;
  }
  .toggle_btn span {
    display: block;
    position: absolute;
    left: 0;
    width: 30px;
    height: 4px;
    
    border-radius: 4px;
    transition: all .5s;
  }
  .toggle_btn span:nth-child(1) {
    top: 4px;
  }
  .toggle_btn span:nth-child(2) {
    top: 14px;
  }
  .toggle_btn span:nth-child(3) {
    bottom: 2.5px;
  }
  .open .toggle_btn span {
    background-color: #fff;
  }
  .open .toggle_btn span:nth-child(1) {
    -webkit-transform: translateY(10px) rotate(-315deg);
    transform: translateY(10px) rotate(-315deg);
  }
  .open .toggle_btn span:nth-child(2) {
    opacity: 0;
  }
  .open .toggle_btn span:nth-child(3) {
    -webkit-transform: translateY(-10px) rotate(315deg);
    transform: translateY(-10px) rotate(315deg);
  }
  
  #mask {
    display: none;
    transition: all .5s;
  }
  .open #mask {
    display: block;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #000;
    opacity: .8;
    z-index: 2;
    cursor: pointer;
  }