.btn {
    display: inline-block;
    vertical-align: top;
    padding: 8px 30px;
    border: 3px solid #fff;
    font-size: 16px;
    font-weight: 700;
    color: #fff;
    text-transform: uppercase;
    text-decoration: none;
    transition: background .1s linear, color .1s linear;
}

.btn:hover {
    background-color: #fff;
    color: #333;
}