button, input, select {
    width: 100%;
    height: 100%;
}
td {
    width: 20%;
}
.grid {
    margin-top: 20px;
    margin-bottom: 20px;
}
footer {
    text-align: center;
}
.parent, .timer {
    display: grid;
    grid-column-gap: 20px;
    grid-row-gap: 20px;
    margin-top: 20px;
    margin-bottom: 20px;
    grid-auto-columns: 1fr;
    grid-auto-rows: 1fr;
}
@media (min-width: 900px) {
    table {
        font-size: xx-large;
    }
    .parent {
        grid-template-columns: repeat(4, 1fr);
    }
    .timer {
        grid-template-columns: 4fr repeat(2, 1fr);
    }
}