3D DOM viewer, copy-paste this into your console to visualise the DOM topographically.

DOM3D-1line.js

(()=>{const SHOW_SIDES=false;const COLOR_SURFACE=false;const COLOR_RANDOM=false;const COLOR_HUE=190;const MAX_ROTATION=180;const THICKNESS=20;const DISTANCE=10000;function getRandomColor(){const hue=Math.floor(Math.random()*360);const saturation=50+Math.floor(Math.random()*30);const lightness=40+Math.floor(Math.random()*30);return`hsl(${hue},${saturation}%,${lightness}%)`;}const getDOMDepth=element=>[...element.children].reduce((max,child)=>Math.max(max,getDOMDepth(child)),0)+1;const domDepthCache=getDOMDepth(document.body);const getColorByDepth=(depth,hue=0,lighten=0)=>`hsl(${hue},75%,${Math.min(10+depth*(1+60/domDepthCache),90)+lighten}%)`;const body=document.body;body.style.overflow="visible";body.style.transformStyle="preserve-3d";body.style.perspective=DISTANCE;const perspectiveOriginX=(window.innerWidth/2);const perspectiveOriginY=(window.innerHeight/2);body.style.perspectiveOrigin=body.style.transformOrigin=`${perspectiveOriginX}px${perspectiveOriginY}px`;traverseDOM(body,0,0,0);document.addEventListener("mousemove",(event)=>{const rotationY=(MAX_ROTATION*(1-event.screenY/screen.height)-(MAX_ROTATION/2));const rotationX=(MAX_ROTATION*event.screenX/screen.width-(MAX_ROTATION/2));body.style.transform=`rotateX(${rotationY}deg)rotateY(${rotationX}deg)`;});function createSideFaces(element,color){if(!SHOW_SIDES)return;const width=element.offsetWidth;const height=element.offsetHeight;const fragment=document.createDocumentFragment();const createFace=({width,height,transform,transformOrigin,top,left,right,bottom})=>{const face=document.createElement('div');face.className='dom-3d-side-face';Object.assign(face.style,{transformStyle:"preserve-3d",backfaceVisibility:'hidden',position:'absolute',width:`${width}px`,height:`${height}px`,background:color,transform,transformOrigin,overflow:'hidden',willChange:'transform',top,left,right,bottom});fragment.appendChild(face);};createFace({width,height:THICKNESS,transform:`rotateX(-270deg)translateY(${-THICKNESS}px)`,transformOrigin:'top',top:'0px',left:'0px',});createFace({width:THICKNESS,height,transform:'rotateY(90deg)',transformOrigin:'left',top:'0px',left:`${width}px`});createFace({width,height:THICKNESS,transform:`rotateX(-90deg)translateY(${THICKNESS}px)`,transformOrigin:'bottom',bottom:'0px',left:'0px'});createFace({width:THICKNESS,height,transform:`translateX(${-THICKNESS}px)rotateY(-90deg)`,transformOrigin:'right',top:'0px',left:'0px'});element.appendChild(fragment);}function traverseDOM(parentNode,depthLevel,offsetX,offsetY){for(let children=parentNode.childNodes,childrenCount=children.length,i=0;i<childrenCount;i++){const childNode=children[i];if(!(1===childNode.nodeType&&!childNode.classList.contains('dom-3d-side-face')))continue;const color=COLOR_RANDOM?getRandomColor():getColorByDepth(depthLevel,190,-5);Object.assign(childNode.style,{transform:`translateZ(${THICKNESS}px)`,overflow:"visible",backfaceVisibility:"hidden",transformStyle:"preserve-3d",backgroundColor:COLOR_SURFACE?color:getComputedStyle(childNode).backgroundColor,willChange:'transform',});let updatedOffsetX=offsetX;let updatedOffsetY=offsetY;if(childNode.offsetParent===parentNode){updatedOffsetX+=parentNode.offsetLeft;updatedOffsetY+=parentNode.offsetTop;}createSideFaces(childNode,color);traverseDOM(childNode,depthLevel+1,updatedOffsetX,updatedOffsetY);}}})()

To play an April Fools' Day prank:

1. (Review this code on your computer to make sure I'm not doing anything nefarious)
2. Go to family/friend/coworker's unlocked computer
3. Open a new tab and go to https://tinyurl.com/dom3djs
4. Copy that code
5. Close that tab
6. Go to an oft-used tab (webmail is great)
7. Press F12 or Ctrl+Shift+i to get to the Developer Tools Javascript console
8. Paste the code and hit Enter
9. Close the console
10. Be sure not to mouse over the tab you've altered
11. (If you did, reload the page and go back to step 7)

This should take under a minute. Practice if time is an issue.
(Yes, if you're fully thorough, you should review the shortened link's target to ensure you've vetted the right code.)