Tubio/goodies/chrome-extension/popup/css/button.css

button {
    padding: 0.5em 2em;
    color: #04254e;
    font-size: 14pt;
    border-radius: 5px;
    cursor: pointer;
    transition:
        color 0.15s ease,
        transform 0.15s ease;
}

button.small {
    padding: 0.15em 1em;
}

button:hover {
    transform: scale(1.075);
    color: #fff;
    background-color: #5954a4;
}

button.special:hover {
    /*background-color: #5954a4;*/
    color: #fff;
    animation: color-cycle;
    animation-duration: 1s;
    animation-iteration-count: infinite;
}

button.lock {
    visibility: hidden;
}

@keyframes color-cycle {
    0%      {background-color: #ff6666; transform: scale(1.075);}
    16.67%  {background-color: #c966ff;}
    33.33%  {background-color: #6678ff;}
    50%     {background-color: #66edff; transform: scale(1.15);}
    66.66%  {background-color: #66ff70;}
    83.33%  {background-color: #fcff66;}
    100%    {background-color: #ff6666; transform: scale(1.075);}
}