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.