.apst-wrapper,
.apst-wrapper::before,
.apst-wrapper::after,
.apst-wrapper *,
.apst-wrapper *::before,
.apst-wrapper *::after {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    -ms-box-sizing: border-box;
    -o-box-sizing: border-box;
    box-sizing: border-box;
}

.apst-wrapper {
    display: none;
    position: fixed;
    z-index: 99999;
    cursor: pointer;
    box-sizing: border-box;
    /* No blue highlight when clicking on element on mobile devices */
    -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
    -webkit-tap-highlight-color: transparent;
    -webkit-touch-callout: none;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
}

.apst-top {
    top: 20px;
}

.apst-bottom {
    bottom: 20px;
}

.apst-left {
    left: 20px;
}

.apst-center {
    left: 50%;
    margin-left: -40px;
}

.apst-right {
    right: 20px;
}

.apst-button {
    display: block;
    position: relative;
    width: 40px;
    height: 40px;
    background-color: #555;
    -webkit-border-radius: 50%;
    -moz-border-radius: 50%;
    -ms-border-radius: 50%;
    -o-border-radius: 50%;
    border-radius: 50%;
    -webkit-transition: all 0.2s;
    -moz-transition: all 0.2s;
    -ms-transition: all 0.2s;
    -o-transition: all 0.2s;
    transition: all 0.2s;
}

    .apst-button::before {
        content: "";
        display: block;
        position: relative;
        left: 13px;
        top: 14px;
        width: 15px;
        height: 15px;
        border-right: 6px solid white;
        border-top: 6px solid white;
        -webkit-transform: rotate(-45deg);
        -moz-transform: rotate(-45deg);
        -ms-transform: rotate(-45deg);
        -o-transform: rotate(-45deg);
        transform: rotate(-45deg);
        -webkit-transition: all 0.2s;
        -moz-transition: all 0.2s;
        -ms-transition: all 0.2s;
        -o-transition: all 0.2s;
        transition: all 0.2s;
    }

    .apst-button:hover {
        background-color: #333;
    }

        .apst-button:hover::before {
            border-color: white;
        }

@media only screen and (max-width: 640px) {
    .apst-center {
        margin-left: -35px;
    }

    .apst-button {
        width: 70px;
        height: 70px;
    }

        .apst-button::before {
            left: 25px;
            top: 27px;
            width: 20px;
            height: 20px;
        }
}

@media only screen and (max-width: 400px) {
    .apst-center {
        margin-left: -30px;
    }

    .apst-button {
        width: 60px;
        height: 60px;
    }

        .apst-button::before {
            left: 21px;
            top: 23px;
            width: 18px;
            height: 18px;
            border-width: 5px;
        }
}