html, page {  
height: 100vh;
min-height: 100%;
overflow: hidden;
width: 100vw;
min-width: 100%;
}
.box-cover {
border: 0;
position:absolute;
top:0; left:0;
right:0;
bottom:0;
background-color: #fff;
z-index: 10000;
overflow: hidden;
margin: 0;
padding: 0;
width: 100%;
}
.cover-frame {
background-color: #333;
overflow: hidden;
margin: 0;
padding: 0;
width: 100%;
height: 100%;
}
.a-button {
padding: 10px;
background-color: #999;
color: #fff;
border-radius: 4px;
}