The idea of constructing this underwater world came from an animation I watched when I was a child, called Future Boy Conan, which tells the story of the protagonist and his grandfather living on an island after more than half of the earth’s land was destroyed in a war. In the early stages of the story, the underwater ruins are impressive, this scenario may be as anti-war propaganda, perhaps can make people recall childhood memories, or can be as simple as an experience of visiting ruins in the underwater world, after all, visiting underwater ruins is almost impossible in the real world.<br>

基于nginx的 valid_referer变量可以实现这一功能。<br> referer是http协议request header中的一个字段，这个字段可以简单的理解为“经手人”，当我们访问某个网站时，我们向这个网站的nginx web server发起了请求，请求解析完成后 nginx会将各种资源和源代码返回给客户端并进行渲染，因此，我们访问的网站可以被视为是我们访问这些静态文件的“经手人”。通过对referer进行限制，可以防止第三方对于资源的获取。<br>