style.css

html,
body{
    height:100%;
}
#area{
    background:#222 url('img/computer.jpg')center center no-repeat;
    background-size:cover;
    color:white;
    height:100%;
    text-align: center;
    display: flex;
    align-items: center;
}
.container{
    align-items: center;
   margin-left: 350px;
    
}
.col-sm-8{
    font-size: 40px;
    text-align: center;
    margin-right: 100px;
    font-weight: 400;
    font-family: cursive;
    
    
}
hr{
    border-color: blueviolet;
    border-width: 1px;
    margin-top: 20px;

}

.btn{
    background-color: tomato;
    border-radius: 10px;
    border-color: black;
    font-size: 20px;
    box-shadow: 10 10 10 #333;
    background: linear-gradient(#fc3,#f91);
    text-shadow: 0 1px 2px rgba(0,0,0,0.6);
    margin-left: 35%;
}

.btn:hover{
    position:relative;
    
    background-color: burlywood;
    border-radius:20px;
    background: linear-gradient(to top,#fc3,#f91);
    
}
.btn:active{
    position:relative;
    padding-bottom:13px;
    background-color: blue;
    border-radius:20px; 
}