style.css

*{
    box-sizing: border-box;
}
body {

    font-size: 20px;
    align-content: center;
    background: radial-gradient(#81ecec, #00cec9);
    color: white;
}
button{
    background-color: white;
    border-radius: 5px;
    border: 2px solid #81ecec;
    color: #81ecec;
}
#test{
    border: 2px dashed white;
    border-radius: 10px;
    padding: 30px;
    margin: 30px;
}
h3{
    margin: 50px;
    text-align: center;
}