html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
    background-color: #000000;
    display: flex;
    justify-content: center;
    align-items: center;
}

.toolbar {
    display: flex;
    margin: 1rem 0rem;
    height: 2.1rem; /* This needs to be ".toolbar-button height" + ".toolbar-button:hover vertical margin" */
}

.toolbar-button {
    flex-grow: 1;
    height: 2rem;
    border: none;
    outline: none;
    color: #bdc3c7;
    background-color: #34495e;

    transition: background-color 125ms ease-in-out;
    transition: margin-top 50ms ease-in-out;
}

.toolbar-button:hover {
    background-color: #2c3e50;
    margin-top: 0.1rem;
}