CSS code as shown in above video:
/* Make the image bounce when you hover over it */
.hover-bounce img:not(.wp-smiley) {
display: inline-block;
vertical-align: middle;
transform: perspective(1px) translateZ(0);
box-shadow: 0 0 1px rgba(0, 0, 0, 0);
transition-duration: 0.5s;
}
.hover-bounce img:not(.wp-smiley):hover,
.hover-bounce img:not(.wp-smiley):focus,
.hover-bounce img:not(.wp-smiley):active {
transform: scale(0.8);
transition-timing-function: cubic-bezier(0.47, 2.02, 0.31, -0.36);
}