Code sample for my Medium article: You Should Style the Wrong Button State

pulse-effect.css

/* PULSE EFFECT */

button::before {
    content: " ";
    position: absolute;
    top: 1px;
    bottom: 1px;
    left: 1px;
    right: 1px;

    border-radius: 10px;
    background-color: hsla(230, 80%, 80%, 1);
    opacity: 1;

    z-index: -1;
    pointer-events: none;
}

button:not(:active)::before {
    transition: all 0.3s ease-out, opacity 0.2s 0.1s ease-out;

    top: -20px;
    bottom: -20px;
    left: -20px;
    right: -20px;

    opacity: 0;
}