Minimal Lit Element Starter

index.html

<!--
  mkdir hello-world
  cd hello-world
  npm init -y
  npm i es-module-shims lit-element
  curl -O https://gist.githubusercontent.com/pinkhominid/301007797a306c949770f24f2a74c9a8/raw/b963f6205c2436f994b7e32182247d9a1cf1aba5/index.html
  npm i -D http-server
  npx http-server -o
-->
<script defer src="./node_modules/es-module-shims/dist/es-module-shims.js"></script>
<script type="importmap-shim">
  {
    "imports": {
      "lit-html": "./node_modules/lit-html/lit-html.js",
      "lit-html/": "./node_modules/lit-html/",
      "lit-element": "./node_modules/lit-element/lit-element.js"
    }
  }
</script>
<script type="module-shim">
  import { LitElement, html, css } from 'lit-element'

  class HelloWorldElem extends LitElement {
    render() {
      return html`
        <p>Hello World!</p>
      `
    }
  }

  customElements.define('hello-world', HelloWorldElem)
</script>
<hello-world></hello-world>