.box_main{
    width: 80rpx;height: 80rpx; background-color: #fff; border-radius: 50%; border: 1rpx solid #adadad; position: fixed;right: 0; top:50%;
    background-repeat: no-repeat;background-position: center center; background-size: cover;
}
button.control[plain] {
    border: 0;
}