html中如何用其他样式覆盖传输文件标签

<form action="/upload.html/" method="post" novalidate enctype="multipart/form-data">
{#    上传文件时需要添加enctype="multipart/form-data"#}
    {% csrf_token %}
    <input type="text" name="user">
    <div style="position: relative">
        <a>NB的上传</a>
        <input type="file" name="img" style="opacity: 0.2;position: absolute;top: 0;left: 0;">
{#        opacity: 0.2  透明度#}
    </div>


    <input type="submit" value="提交">
</form>