SOURCE

<a href="" class="third-party third-party-weixin">
     <i></i>
     <span></span>
 </a>

.third-party {
    position: relative;
    // 为了兼容firefox必须要变成block或inline-block
    display: inline-block;
    width: 48px;
    height: 48px;
    margin: {
        left: 6%;
        right: 6%;
    }
    &:hover {
        i {
            &::after {
                transform: scale(1);
            }
        }
    }
    span {
        // position: relative是为了兼容firefox和IE
        position: relative;
        display: block;
        width: 48px;
        height: 48px;
        background-size: 30px;
        background-position: center;
        background-repeat: no-repeat;
    }
    i {
        position: absolute;
        top: 0;
        left: 0;
        width: 48px;
        height: 48px;
        &::before {
            content: '';
            border-radius: 50%;
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
        }
        &::after {
            content: '';
            transition: all .3s;
            border-radius: 50%;
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            transform: scale(0);
        }
    }
    &.third-party-weixin {
        span {
            background-image: url(data:image/png;base64,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);
        }
        i {
            &::before {
                background-color: #20a839;
            }
            &::after {
                background-color: #30cc54;
            }
        }
    }
}