You could try minify the javascript (I did it) and inject the shortened version into the custom code area before the end of the tag as the script now only “weights” 7827 characters 
HTML
<canvas id="swarm"></canvas>
Libraries
<script src="https://codepen.io/ImagineProgramming/pen/bcmyD.js"></script>
<script src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/188512/codepen-utilities.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/stats.js/r11/Stats.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/dat-gui/0.5.1/dat.gui.min.js"></script>
Minified JavaScript
<script>
!function(t){"use strict";var i=function(t,i,e){this.set(t,i,e)},e=i.prototype;e.dot2d=function(t,i){return this.x*t+this.y*i},e.dot3d=function(t,i,e){return this.x*t+this.y*i+this.z*e},e.set=function(t,i,e){return this.x=t,this.y=i,this.z=e,this},e.add=function(t){return"number"==typeof t?(this.x+=t,this.y+=t,this.z+=t,this):(this.x+=t.x,this.y+=t.y,this.z+=t.z,this)},e.sub=function(t){return"number"==typeof t?(this.x-=t,this.y-=t,this.z-=t,this):(this.x-=t.x,this.y-=t.y,this.z-=t.z,this)},e.mul=function(t){return"number"==typeof t?(this.x*=t,this.y*=t,this.z*=t,this):(this.x*=t.x,this.y*=t.y,this.z*=t.z,this)},e.div=function(t){return"number"==typeof t?(this.x/=t,this.y/=t,this.z/=t,this):(this.x/=t.x,this.y/=t.y,this.z/=t.z,this)},e.move=function(t){return t instanceof i&&(t.x=this.x,t.y=this.y,t.z=this.z),this},e.within2d=function(t){return this.x>=0&&this.x<t.x&&this.y>=0&&this.y<t.y},e.wrap2d=function(t){return this.x>t.x?(this.x=0,!0):this.x<0?(this.x=t.x,!0):this.y>t.y?(this.y=0,!0):this.y<0?(this.y=t.y,!0):void 0},e.eq=function(t){return t instanceof i&&this.x===t.x&&this.y===t.y&&this.z===t.z},e.distance=function(t){var i=this.x-t.x,e=this.y-t.y;return Math.sqrt(i*i+e*e)},e.clone=function(){return new i(this.x,this.y,this.z)},t.Vector3D=i}(window),function(t){"use strict";var i=function(){this.grad3=[new Vector3D(1,1,0),new Vector3D(-1,1,0),new Vector3D(1,-1,0),new Vector3D(-1,-1,0),new Vector3D(1,0,1),new Vector3D(-1,0,1),new Vector3D(1,0,-1),new Vector3D(-1,0,-1),new Vector3D(0,1,1),new Vector3D(0,-1,1),new Vector3D(0,1,-1),new Vector3D(0,-1,-1)],this.p=[151,160,137,91,90,15,131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,190,6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,88,237,149,56,87,174,20,125,136,171,168,68,175,74,165,71,134,139,48,27,166,77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,102,143,54,65,25,63,161,1,216,80,73,209,76,132,187,208,89,18,169,200,196,135,130,116,188,159,86,164,100,109,198,173,186,3,64,52,217,226,250,124,123,5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,223,183,170,213,119,248,152,2,44,154,163,70,221,153,101,155,167,43,172,9,129,22,39,253,19,98,108,110,79,113,224,232,178,185,112,104,218,246,97,228,251,34,242,193,238,210,144,12,191,179,162,241,81,51,145,235,249,14,239,107,49,192,214,31,181,199,106,157,184,84,204,176,115,121,50,45,127,4,150,254,138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180],this.permutation=new Array(512),this.gradP=new Array(512),this.F2=.5*(Math.sqrt(3)-1),this.G2=(3-Math.sqrt(3))/6,this.F3=1/3,this.G3=1/6},e=i.prototype;e.init=function(t){if("function"!=typeof t)throw new TypeError("prng needs to be a function returning an int between 0 and 255");for(var i=0;i<256;i+=1){var e=this.p[i]^t();this.permutation[i]=this.permutation[i+256]=e,this.gradP[i]=this.gradP[i+256]=this.grad3[e%this.grad3.length]}},e.simplex3d=function(t,i,e){var n,s,o,r,h,a,l,d,c,u,p,f,m,y,w,g,v,x,b,D,C,z,M,V=(t+i+e)*this.F3,P=Math.floor(t+V),G=Math.floor(i+V),E=Math.floor(e+V),S=(P+G+E)*this.G3,L=t-P+S,T=i-G+S,F=e-E+S;return L>=T?T>=F?(n=1,s=0,o=0,r=1,h=1,a=0):L>=F?(n=1,s=0,o=0,r=1,h=0,a=1):(n=0,s=0,o=1,r=1,h=0,a=1):T<F?(n=0,s=0,o=1,r=0,h=1,a=1):L<F?(n=0,s=1,o=0,r=0,h=1,a=1):(n=0,s=1,o=0,r=1,h=1,a=0),l=L-n+this.G3,d=T-s+this.G3,c=F-o+this.G3,u=L-r+2*this.G3,p=T-h+2*this.G3,f=F-a+2*this.G3,m=L-1+3*this.G3,y=T-1+3*this.G3,w=F-1+3*this.G3,P&=255,G&=255,E&=255,g=this.gradP[P+this.permutation[G+this.permutation[E]]],v=this.gradP[P+n+this.permutation[G+s+this.permutation[E+o]]],x=this.gradP[P+r+this.permutation[G+h+this.permutation[E+a]]],b=this.gradP[P+1+this.permutation[G+1+this.permutation[E+1]]],C=.6-l*l-d*d-c*c,z=.6-u*u-p*p-f*f,M=.6-m*m-y*y-w*w,32*(((D=.6-L*L-T*T-F*F)<0?0:(D*=D)*D*g.dot3d(L,T,F))+(C<0?0:(C*=C)*C*v.dot3d(l,d,c))+(z<0?0:(z*=z)*z*x.dot3d(u,p,f))+(M<0?0:(M*=M)*M*b.dot3d(m,y,w)))},t.Perlin=i}(window),function(t){"use strict";window.MouseMonitor=function(t){this.position=new Vector3D(0,0,0),this.state={left:!1,middle:!1,right:!1},this.element=t;var i=this;t.addEventListener("mousemove",function(t){var e,n,s;null==(t=t||window.event).pageX&&null!=t.clientX&&(n=(e=t.target&&t.target.ownerDocument||document).documentElement,s=e.body,t.pageX=t.clientX+(n&&n.scrollLeft||s&&s.scrollLeft||0)-(n&&n.clientLeft||s&&s.clientLeft||0),t.pageY=t.clientY+(n&&n.scrollTop||s&&s.scrollTop||0)-(n&&n.clientTop||s&&s.clientTop||0)),i.position.x=t.pageX,i.position.y=t.pageY}),t.addEventListener("contextmenu",function(t){return t.preventDefault()}),t.addEventListener("mousedown",function(t){return 1===t.which&&(i.state.left=!0),2===t.which&&(i.state.middle=!0),3===t.which&&(i.state.right=!0),t.preventDefault()}),t.addEventListener("mouseup",function(t){return i.state.left=i.state.middle=i.state.right=!1,t.preventDefault()})}}(),function(t){"use strict";var i=function(t,i,e,n){this.p=new Vector3D,this.t=new Vector3D,this.v=new Vector3D,this.g=t,this.b=i,this.r=e,this.m=n,this.reset()},e=i.prototype;e.reset=function(){this.p.x=this.t.x=Math.floor(this.r.random()*this.b.x),this.p.y=this.t.y=Math.floor(this.r.random()*this.b.y),this.v.set(1,1,0),this.i=0,this.l=this.r.random(1e3,1e4)},e.step=function(){this.i++>this.l&&this.reset();var t=this.p.x/200,i=this.p.y/200,e=Date.now()/5e3,n=this.r.random()*Math.Tau,s=this.r.random()/4;if(this.v.x+=s*Math.sin(n)+this.g.simplex3d(t,i,-e),this.v.y+=s*Math.cos(n)+this.g.simplex3d(t,i,e),this.m.state.left&&this.v.add(this.m.position.clone().sub(this.p).mul(85e-5)),this.m.state.right&&this.p.distance(this.m.position)<this.r.random(200,250)&&this.v.add(this.p.clone().sub(this.m.position).mul(.02)),this.m.state.middle){var o=this.p.distance(this.m.position),r=this.r.random(200,250);o<r&&this.v.mul(o/r)}this.p.move(this.t).add(this.v.mul(.94)),this.p.wrap2d(this.b)&&this.p.move(this.t)},e.render=function(t){t.moveTo(this.t.x,this.t.y),t.lineTo(this.p.x,this.p.y)},t.Particle=i}(window),window.addEventListener("load",function(){var t,i,e,n=new SmallPRNG(+new Date),s=new Perlin,o=document.getElementById("swarm"),r=o.getContext("2d"),h=new Stats,a=new MouseMonitor(o),l=new dat.GUI,d=0,c=[],u=new Vector3D(0,0,0),p={particleNum:5e3,fadeOverlay:!0,rotateColor:!0,staticColor:{r:0,g:75,b:50},staticColorString:"rgba(0, 75, 50, 0.55)"};h.setMode(0),h.domElement.style.position="absolute",h.domElement.style.right="5px",h.domElement.style.bottom="5px",document.body.appendChild(h.domElement);var f=l.addFolder("Particles"),m=l.addFolder("Colors");f.add(p,"particleNum",1e3,15e3).step(10).name("Particles").onChange(function(){if(p.particleNum<c.length){var t=c.length-p.particleNum;c.splice(c.length-t,t)}else for(var i=c.length;i<p.particleNum;i+=1)c.push(new Particle(s,u,n,a))}),m.add(p,"fadeOverlay").name("Fade Clear").onChange(function(){p.fadeOverlay&&t()}),m.add(p,"rotateColor").name("Rotate Color"),m.addColor(p,"staticColor").name("Static Color").onChange(function(){p.staticColorString="rgba("+Math.floor(p.staticColor.r)+", "+Math.floor(p.staticColor.g)+", "+Math.floor(p.staticColor.b)+", 0.55)"}),f.open(),m.open(),l.close(),s.init(function(){return n.random(0,255)}),(t=function(){o.width=i=u.x=window.innerWidth,o.height=e=u.y=window.innerHeight,r.fillStyle="#ffffff",r.fillRect(0,0,i,e)})(),window.addEventListener("resize",t);for(var y=0;y<p.particleNum;y+=1)c.push(new Particle(s,u,n,a));!function t(){requestAnimFrame(t),h.begin(),r.beginPath();for(var n=0;n<c.length;n+=1)c[n].step(),c[n].render(r);r.globalCompositeOperation="source-over",p.fadeOverlay?r.fillStyle="rgba(0, 0, 0, .085)":r.fillStyle="rgba(0, 0, 0, 1)",r.fillRect(0,0,i,e),r.globalCompositeOperation="lighter",p.rotateColor?r.strokeStyle="hsla("+d+", 75%, 50%, .55)":r.strokeStyle=p.staticColorString,r.stroke(),r.closePath(),h.end(),d=(d+.5)%360}()});
</script>
Hope that helps.
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