.contact, .contact-email, .contact-wechat, .contact-weibo {
    display: inline-block;
    width: 26px;
    height: 26px;
    line-height: 10em;
    text-indent: -9999px;
    overflow: hidden;
    background: url(../asset/icon_contact.png) no-repeat;
    background-position-x: 0%;
    background-position-y: 0%;
    background-size: 65px;
}
.contact-weibo {
    background-position: -40px -60px;
}

.contact.contact-weibo:hover {
    background-position: 0 -60px;
}
.contact-wechat {
    background-position: -40px 0;
}

.contact.contact-wechat:hover {
    background-position: 0 0;
}

@media only screen and (max-width: 400px) {
    .icons .icon {   
        font-size: 4rem;
    }
}

@media only screen and (min-width: 401px) {
    .icons .icon {   
        font-size: 6rem;
    }
}

.icon {
    color: black
}
.icon:hover {
    color: #888
}
.icons p {
    margin-top: 1rem;
}
.centered {
    text-align: center;
}
.download-section, .ad-section, .service-section {
    padding: 3rem 0;
}
.bg-matlab {
    background-size:100% norepeat;
    background-image: url("../asset/matlab-bg.png");
}
.bg-grey {
    background-color: hsl(0, 0%, 97%) !important;
}
.matlab-img {
    width: 16rem;
    height: 16rem;
}
footer {
    background-color: #fafafa;
    padding: 3rem 1.5rem 6rem;
}