Document

*{

margin: 0;

padding: 0;

}

div{

position: absolute; 

top: 50%; 

left:50%; 

margin: -150px 0 0 -150px; 

width: 300px; 

height: 300px;

}

input{

width:298px;

height: 30px;

border: 1px solid black;

margin-top: 30px;

}

button{

width:298px;

height: 30px;

border: 1px solid black;

margin-top: 30px;

box-sizing: content-box;

border-radius: 10px;

}