body{

background:#111;
color:#00ff00;
font-family:Consolas;
text-align:center;

}

.contenedor{

width:600px;
margin:auto;
margin-top:40px;
padding:20px;
border:2px solid #00ff00;
border-radius:10px;

}

input{

width:220px;
padding:10px;
font-size:20px;
text-align:center;

}

button{

padding:10px 30px;
font-size:18px;
cursor:pointer;

}

pre{

font-size:18px;
line-height:18px;

}