a.button21 {
    display: inline-block;
    width: auto;
    height: auto;
    margin-bottom: 10px;
    margin-top: 10px;
    margin-left: 20px;
    padding-left: 5px;
    padding-right: 5px;
    line-height: 2em;
    vertical-align: middle;
    text-align: center;
    text-decoration: none;
    user-select: none;
    color: rgb(0,0,0);
    outline: none;
    border: 1px solid rgba(0,0,0,.4);
    border-top-color: rgba(0,0,0,.3);
    border-radius: 2px;
    background: linear-gradient(rgb(255,255,255), rgb(240,240,240));
    box-shadow:
        0 0 3px rgba(0,0,0,0) inset,
        0 1px 1px 1px rgba(255,255,255,.2),
        0 -1px 1px 1px rgba(0,0,0,0);
    transition: .2s ease-in-out;
}
a.button21:hover:not(:active) {
    box-shadow:
        0 0 3px rgba(0,0,0,0) inset,
        0 1px 1px 1px rgba(0,255,255,.5),
        0 -1px 1px 1px rgba(0,255,255,.5);
}
a.button21:active {
    background: linear-gradient(rgb(250,250,250), rgb(235,235,235));
    box-shadow:
        0 0 3px rgba(0,0,0,.5) inset,
        0 1px 1px 1px rgba(255,255,255,.4),
        0 -1px 1px 1px rgba(0,0,0,.1);
}