html,body{
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
}
div{
  margin: 0;
  padding: 0;
}
#mask{
  display: none;
  position: fixed;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  z-index: 999;
  background-color: rgba(0, 0, 0, 0.3);
}
#mask>div{
  width: 343px;
  box-shadow: rgba(0, 0, 0, 0.5) 0px 0px 10px 0px;
  background-color: #fff;
  color: #333;
  min-height: 280px;
  position: fixed;
  top: 30%;
  left: 40%;
  z-index: 999;
  transform: translateX(-40%);
}
#ul{
  height: 250px;
  overflow-x: hidden;
  overflow-y: auto;
  list-style: none;
  padding: 0 10px;
}
.foot {
  font-size: 28upx;
  padding: 8upx 15upx;
  color: #999999;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  background: #f0f0f0;
}
#ul li:hover {
  background-color: #eee;
}

.btn{
  position: absolute;
  top: 0;
  left: 0;
}
ul, li{
  list-style: none;
}