body {
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: .5rem;
}

h1 {
    border-bottom: 5px double forestgreen;
    flex-grow: 1;
    text-align: center;
    padding-bottom: .66rem;
}

table {
    border-spacing:0;
    border-collapse: collapse;
}
td, th {
    padding: .5rem 0;
    text-align: center;
}
tbody > tr {
    border-top: 1px solid #222;
}
tbody > tr:nth-child(odd) {
    background: #bbb;
}
tbody > tr:nth-child(even) {
    background: #ddd;
}