my-404.js

import { PolymerElement, html } from "@polymer/polymer/polymer-element.js";
class My404 extends PolymerElement {
  static get template() {
    return html`
      <style>
        :host {
          display: flex;
          text-align: center;
          flex-direction: column;
          align-items: center;
          justify-content: center;
          padding: 32px;
        }
        h2 {
          font-size: 2em;
          margin: 0;
        }
        h3 {
          font-size: 1em;
          margin: 16px 0;
          color: #b2b2b2;
        }
        paper-fab {
          color: var(--primary-color);
        }
      </style>
      <h2>404</h2>
      <h3>Page not found!</h3>
      <div>
        <a href="/"
          ><paper-fab icon="my-icons:arrow-back" aria-label="Back"></paper-fab
        ></a>
      </div>
    `;
  }
}
window.customElements.define("my-404", My404);