h1 {
    background-color: powderblue;
}

.td_left {
    text-align: center;
    /* left-side image is bigger, thus cannot use 50% */
    /* width: 50% */
}

.td_right {
    text-align: center;
    /* width: 50%; */
}

a img {
    transition-property: width, opacity, grayscale, saturate, border;
    transition-duration: 2s;
    width: 85%;
    opacity: 0.8;
    filter: grayscale(30%);
    filter: saturate(90%);
    border: solid 1px red;
}

a img:hover {
    border: solid 5px red;
    width: 102%;
    opacity: 1.0;
    filter: grayscale(0%);
    filter: saturate(110%);
}