.btn-wsp {
    position: fixed;
    width: 60px;
    height: 60px;
    line-height: 63px;
    bottom: 10px;
    right: 43px;
    background: #25d366;
    color: #FFF;
    border-radius: 50px;
    text-align: center;
    font-size: 35px;
    box-shadow: 0px 1px 10px rgba(0, 0, 0, 0.3);
    z-index: 100;
    transition: all 300ms ease;
}

.btn-wsp:hover {
    background: #20ba5a;
}

@media only screen and (max-width: 575px) {
    .btn-wsp {
        right: 23px;
        bottom: 5px;
    }
}

@media only screen and (max-width: 479px) {
    .btn-wsp {
        bottom: 5px;
    }
}

@media only screen and (max-width: 359px) {
    .btn-wsp {
        font-size: 18px;
        height: 30px;
        line-height: 32px;
        width: 30px;
        bottom: 20px;
        right: 28px;
    }
}