main {
    box-shadow: 0px 0px 1px;
    width: 100%;
    max-width: 450px;
    box-sizing: border-box;
    padding: 20px auto;
    margin: 20px auto;
    text-align: center;
    height: 250px;
}
header {
    background-color: limegreen;
    color: white;
}
header h2,
p {
    margin: 0px;
}
main label,
select {
    margin: 10px 0px;
}
button {
    max-width: inherit;
    background-color: limegreen;
    color: white;
    border: none;
    box-shadow: inherit;
    padding: 3px;
    border-radius: 2px;
    cursor: pointer;
    font-weight: 700;
    padding: 5px;
}
#output {
    box-shadow: inherit;
    border: none;
    box-shadow: inherit;
    margin: 20px;
    border-radius: 2px;
    margin: 10px;
}