html, body {
  margin: 0;
  height: 100%;
  width: 100%;
}

.site-header {
  background: #FFF;
  height: 70px;
  width: 100%;
  position: fixed;
  top: 0;
  display: flex;
  z-index: 1000;
  border-bottom: 1px solid #ccc;
}

.topnav-container {
  display:block;
  top: 0;
  height: 70px;
  background-color: rgb(255, 255, 255);
}

.logo {
  margin-left: 20px;
  float: left;
}
.button-div {
  display: none;
  height:70px;
  width:70px;
}

.topnav-button {
  position: relative;
  float: right;
  width: 60px;
  height: 46px;
  margin:12px 20px 12px 0;
  overflow: auto;
  border: 1px solid;
  border-radius: 5px;
  border-color: rgb(0, 0, 0, 0.5);
  background-color: transparent;
}

.topnav-button-bg {
  display: inline-block;
  background-image: url("data:image/svg+xml;charset=utf8,%3Csvg viewBox='0 0 30 30' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath stroke='rgba(0, 0, 0, 1)' stroke-width='2' stroke-linecap='round' stroke-miterlimit='10' d='M4 7h22M4 15h22M4 23h22'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: center;
  width: 30px;
  height: 30px;
  vertical-align: middle;
}

.topnav {
  float: right;
  position: relative;
  height: 70px;
  list-style-type: none;
  top: 0;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: rgb(255, 255, 255);
  opacity: 1;

}

.topnav-item {
  height: 30px;
  cursor: pointer;
  font-family: Microsoft JhengHei;
  display: inline-block;
  color: rgb(0, 0, 0);
  font-size: 20px;
  text-align: center;
  padding: 20px 20px;
  text-decoration: none;
  line-height: 30px;
}

.topnav-item:hover {
  color: rgb(219, 219, 219);
}