a.light-btn.colored span {
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    text-shadow: -1px 2px 1px #5d5d5d;
}

a.light-btn.colored:before {       position: absolute;
    z-index: -10;
    top: 0;
    left: 0;
    display: block;
    width: 100%;
    height: 100%;
    content: '';
    transition: all .35s ease;
    background: linear-gradient(-350deg, #08c6ffcc 0, #00ff72 100%);
}

a.light-btn {
    font-family: Montserrat, "Helvetica Neue", "Lucida Grande", Arial, Verdana, sans-serif;
    font-size: 2rem;
    font-weight: 700;
    position: relative;
    display: inline-flex;
    height: 60px;
    margin: 15px 0 0 0;
    padding: 0 25px;
    text-align: center;
    text-transform: uppercase;
    color: #FFFFFF;
    border: 1px solid #000000;
    border-bottom: 2px solid #91ff00a1;
    border-radius: 5px;
    background: transparent;
    align-items: center;
    justify-content: center;
}


Contribuição By Gabriel da Luz :D