1. 插入Canvas标签

首先打开Butterfly主题的_config.yml文件或者使用HTML直接插入，找到配置文件对应的inject部分，插入

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<canvas id="universe"></canvas>

2. 创建JS文件

在butterfly/source/js/创建一个universe.js文件，或者添加到自己的js文件中

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function dark() {window.requestAnimationFrame=window.requestAnimationFrame||window.mozRequestAnimationFrame||window.webkitRequestAnimationFrame||window.msRequestAnimationFrame;var n,e,i,h,t=.05,s=document.getElementById("universe"),o=!0,a="180,184,240",r="226,225,142",d="226,225,224",c=[];function f(){n=window.innerWidth,e=window.innerHeight,i=.216*n,s.setAttribute("width",n),s.setAttribute("height",e)}function u(){h.clearRect(0,0,n,e);for(var t=c.length,i=0;i<t;i++){var s=c[i];s.move(),s.fadeIn(),s.fadeOut(),s.draw()}}function y(){this.reset=function(){this.giant=m(3),this.comet=!this.giant&&!o&&m(10),this.x=l(0,n-10),this.y=l(0,e),this.r=l(1.1,2.6),this.dx=l(t,6*t)+(this.comet+1-1)*t*l(50,120)+2*t,this.dy=-l(t,6*t)-(this.comet+1-1)*t*l(50,120),this.fadingOut=null,this.fadingIn=!0,this.opacity=0,this.opacityTresh=l(.2,1-.4*(this.comet+1-1)),this.do=l(5e-4,.002)+.001*(this.comet+1-1)},this.fadeIn=function(){this.fadingIn&&(this.fadingIn=!(this.opacity>this.opacityTresh),this.opacity+=this.do)},this.fadeOut=function(){this.fadingOut&&(this.fadingOut=!(this.opacity<0),this.opacity-=this.do/2,(this.x>n||this.y<0)&&(this.fadingOut=!1,this.reset()))},this.draw=function(){if(h.beginPath(),this.giant)h.fillStyle="rgba("+a+","+this.opacity+")",h.arc(this.x,this.y,2,0,2*Math.PI,!1);else if(this.comet){h.fillStyle="rgba("+d+","+this.opacity+")",h.arc(this.x,this.y,1.5,0,2*Math.PI,!1);for(var t=0;t<30;t++)h.fillStyle="rgba("+d+","+(this.opacity-this.opacity/20*t)+")",h.rect(this.x-this.dx/4*t,this.y-this.dy/4*t-2,2,2),h.fill()}else h.fillStyle="rgba("+r+","+this.opacity+")",h.rect(this.x,this.y,this.r,this.r);h.closePath(),h.fill()},this.move=function(){this.x+=this.dx,this.y+=this.dy,!1===this.fadingOut&&this.reset(),(this.x>n-n/4||this.y<0)&&(this.fadingOut=!0)},setTimeout(function(){o=!1},50)}function m(t){return Math.floor(1e3*Math.random())+1<10*t}function l(t,i){return Math.random()*(i-t)+t}f(),window.addEventListener("resize",f,!1),function(){h=s.getContext("2d");for(var t=0;t<i;t++)c[t]=new y,c[t].reset();u()}(),function t(){document.getElementsByTagName('html')[0].getAttribute('data-theme')=='dark'&&u(),window.requestAnimationFrame(t)}()};
dark()

代码的这一部分要求data-theme也就是主题为dark暗色主题，因此仅在暗色主题生效，随后将js文件添加到配置文件的inject处或者其他需要的位置。

3. CSS样式

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/* 背景宇宙星光  */
#universe{
  display: block;
  position: fixed;
  margin: 0;
  padding: 0;
  border: 0;
  outline: 0;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: -1;
}

CSS文件也是添加到配置文件的inject处或者其他需要的位置。

4. 主题配置文件最后如下：

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inject:
  head:
    - <link rel="stylesheet" href="/css/universe.css?1">
  bottom:
    - <canvas id="universe"></canvas>
    - <script defer src="/js/universe.js"></script>