<script>
  if ('paintWorklet' in CSS && 'registerProperty' in CSS && 'CSSUnitValue' in window) {
    CSS.registerProperty({
      name: '--tooth-width',
      syntax: '<length>',
      initialValue: '40px'
    });
    CSS.registerProperty({
      name: '--tooth-height',
      syntax: '<length>',
      initialValue: '20px'
    });

    // load this CodePen's JS file as the paint worklet
    CSS.paintWorklet.addModule('/lonekorean/pen/zWOZyx.js');
  } else {
    document.querySelector('html').classList.add('no-support');
  }
</script>

<div class="container">
  <div class="slot">
    <div class="jagged"></div>
  </div>
  <div class="slot">
    <div class="jagged"></div>
  </div>
</div>

<div class="warning">
  <i class="fas fa-exclamation-triangle"></i><br>
  This Houdini demo requires the <strong>CSS Paint API</strong>, <strong>CSS Properties and Values API</strong>, and <strong>Typed OM</strong>.<br>
  Use <strong>Chrome</strong> and go to <strong>chrome://flags</strong> and enable <strong>Experimental Web Platform features</strong>.<br>
  Also make sure you're serving over <strong>https</strong> or <strong>localhost</strong>.
</div>
*, *::before, *::after {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  margin: 0 40px;
  background: #000;
  font: 1rem/1.25 'Mukta Mahee', sans-serif;
}

.container {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  grid-gap: 40px;
  align-items: center;
  height: 100%;
}

.slot {
  display: flex;
  justify-content: center;
  position: relative;
  height: 300px;
  border: 1px solid #fff;
  background-image: linear-gradient(to right, #444, #000);
}

.jagged {
  --tooth-width: 80px;
  --tooth-height: 30px;
  -webkit-mask-image: paint(jagged-edge);

  position: absolute;
  top: 30%;
  bottom: 0;
  width: 100%;
}

.slot:nth-child(1) .jagged {
  background-image: linear-gradient(to right, #22c1c3, #fdbb2d);
}

.slot:nth-child(2) .jagged {
  /* pixel art from Iconoclasts, fun game! http://www.playiconoclasts.com/ */
  background-image: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/77020/iconoclasts.png');
  background-size: cover;
  background-position: 50% 0;
}

.warning {
  display: none;
  position: absolute;
  top: 10px;
  left: 10px;
  right: 10px;
  padding: 20px;
  border-top: 4px dashed #e8590c;
  background-color: #ffe8cc;
  color: #e8590c;
  text-align: center;
}

.no-support .warning {
  display: block;
}

.warning .fas {
  margin-bottom: 1rem;
  font-size: 1.5rem;
}
/*
This CodePen's JS file has been "hijacked" to serve as the paint worklet file. The if check below ensures the code only runs when referenced as such. JavaScript for the page is at the top of the HTML. I'm only doing this to squeeze everything into one CodePen.

IMPORTANT: If you fork, update the CodePen JS file path in the HTML.

ALSO IMPORTANT: If you edit code here, disable cache and reload. Live preview won't pick up changes in the paint worklet.
*/

if (typeof registerPaint !== 'undefined') {
  class JaggedEdgePainter {
    static get inputProperties() {
      return ['--tooth-width', '--tooth-height'];
    }

    paint(ctx, size, props) {
      let toothWidth = props.get('--tooth-width').value;
      let toothHeight = props.get('--tooth-height').value;

      // lots of math to ensure teeth are collectively centered
      let spaceBeforeCenterTooth = (size.width - toothWidth) / 2;
      let teethBeforeCenterTooth = Math.ceil(spaceBeforeCenterTooth / toothWidth);
      let totalTeeth = teethBeforeCenterTooth * 2 + 1;
      let startX = spaceBeforeCenterTooth - teethBeforeCenterTooth * toothWidth;

      // start drawing teeth from left
      ctx.beginPath();
      ctx.moveTo(startX, toothHeight);

      // draw the top zig-zag for all the teeth
      for (let i = 0; i < totalTeeth; i++) {
        let x = startX + toothWidth * i;
        ctx.lineTo(x + toothWidth / 2, 0);
        ctx.lineTo(x + toothWidth, toothHeight);
      }

      // surround the area below the teeth and fill it all in
      ctx.lineTo(size.width, size.height);
      ctx.lineTo(0, size.height);
      ctx.closePath();
      ctx.fill();
    }
  }

  registerPaint('jagged-edge', JaggedEdgePainter);
}

External CSS

  1. https://fonts.googleapis.com/css?family=Mukta+Mahee:400,700
  2. https://use.fontawesome.com/releases/v5.0.6/css/all.css

External JavaScript

This Pen doesn't use any external JavaScript resources.