table {
    overflow: hidden;
    z-index: 1;
    font-family: monospace;
}

td, th {
    position: relative;
    text-align: center;
    vertical-align: middle;
}

td {
    cursor: pointer;
}

td:hover::before {
    background-color: lightgray;
    content: '\00a0';
    height: 100%;
    left: -5000px;
    position: absolute;
    top: 0;
    width: 10000px;
    z-index: -1;
}

td:hover::after {
    background-color: lightgray;
    content: '\00a0';
    height: 10000px;
    left: 0;
    position: absolute;
    top: -5000px;
    width: 100%;
    z-index: -1;
}