Edit in JSFiddle

<!doctype html>
<html lang="en">

<my-counter></my-counter>

<script type="module">
  import { html } from 'https://unpkg.com/lit-html/lit-html.js';
  import { component, useState } from 'https://unpkg.com/haunted/haunted.js';

  function Counter() {
    const [count, setCount] = useState(0);

    return html`
      <div id="count">${count}</div>
      <button type="button" @click=${() => setCount(count + 1)}>Increment</button>
    `;
  }

  customElements.define('my-counter', component(Counter));
</script>