body {
    margin: 0;
    overflow: hidden;
}

button {
    z-index: 2;
    overflow: hidden;
    background-color: #00b6ff;
    border: none;
    border-radius: 50%;
    background-size: 66%;
    background-position: center;
    background-repeat: no-repeat;
    padding: 0;
    outline: none;

    -webkit-transition: background-color 0.2s;
    -moz-transition: background-color 0.2s;
    -ms-transition: background-color 0.2s;
    -o-transition: background-color 0.2s;
    transition: background-color 0.2s;
}

button:hover {
    background-color: #2eceff;
}

.panel {
    z-index: 1;
    overflow: hidden;
    background-color: white;
    transform: none;
    -webkit-transition: transform 0.2s ease-in-out;
    -moz-transition: transform 0.2s ease-in-out;
    -ms-transition: transform 0.2s ease-in-out;
    -o-transition: transform 0.2s ease-in-out;
    transition: transform 0.2s ease-in-out;
}

.panel.hidden {
    transform: translate(-500px);
}

.shadow {
    box-shadow: rgba(0, 0, 0, 0.5) 0px 1px 4px 0px;
}