.btn, a.btn {
    background-color: #01996D;
    display: inline-block;
    min-height: 51px;
    display: flex;
    justify-content: center;
    align-items: center;
    line-height: 1;
    padding: 0 50px;
    font-size: 20px;
    color: #fff;
    font-weight: 400;
    border-radius: 4px;
    transition: opacity .2s ease;
}

.btn:hover, a.btn:hover {
    opacity: 0.8;
    color: #fff;
}

.btn-big, a.btn-big {
    min-height: 65px;
}

@media (max-width: 991px) {
    .btn, a.btn {
        padding: 0 30px;
        min-height: 41px;
    }

    .btn-big, a.btn-big {
        min-height: 55px;
    }
}