Just the render field

app.re

render: self => {
  let (route, title) = self.state.routeWithTitle;
  <div
    className=("App" ++ (self.state.nav.isOpen ? " overlay" : ""))
    onClick=(_event => self.send(ToggleMenu(false)))>
    <header>
      <a
        onClick=(
          event => {
            ReactEventRe.Mouse.stopPropagation(event);
            self.send(ToggleMenu(! self.state.nav.isOpen));
          }
        )>
        <svg viewBox="0 0 24 24">
          <path
            d="M21 11h-18c-0.6 0-1 0.4-1 1s0.4 1 1 1h18c0.6 0 1-0.4 1-1s-0.4-1-1-1z"
          />
          <path
            d="M3 7h18c0.6 0 1-0.4 1-1s-0.4-1-1-1h-18c-0.6 0-1 0.4-1 1s0.4 1 1 1z"
          />
          <path
            d="M21 17h-18c-0.6 0-1 0.4-1 1s0.4 1 1 1h18c0.6 0 1-0.4 1-1s-0.4-1-1-1z"
          />
        </svg>
      </a>
      <h1> (ReasonReact.stringToElement(title)) </h1>
    </header>
    <nav
      className=(self.state.nav.isOpen ? "active" : "")
      onClick=(event => ReactEventRe.Mouse.stopPropagation(event))>
      <header>
        <a onClick=(_event => self.send(ToggleMenu(false)))>
          <svg viewBox="0 0 32 32">
            <path
              d="M12.586 27.414l-10-10c-0.781-0.781-0.781-2.047 0-2.828l10-10c0.781-0.781 2.047-0.781 2.828 0s0.781 2.047 0 2.828l-6.586 6.586h19.172c1.105 0 2 0.895 2 2s-0.895 2-2 2h-19.172l6.586 6.586c0.39 0.39 0.586 0.902 0.586 1.414s-0.195 1.024-0.586 1.414c-0.781 0.781-2.047 0.781-2.828 0z"
            />
          </svg>
          (ReasonReact.stringToElement(title))
        </a>
        <svg viewBox="0 0 32 32">
          <path
            d="M8 10c0-4.418 3.582-8 8-8s8 3.582 8 8c0 4.418-3.582 8-8 8s-8-3.582-8-8zM24 20h-16c-4.418 0-8 3.582-8 8v2h32v-2c0-4.418-3.582-8-8-8z"
          />
        </svg>
        <p> (ReasonReact.stringToElement(self.state.user.name)) </p>
        <p> (ReasonReact.stringToElement(self.state.user.email)) </p>
      </header>
      <label> (ReasonReact.stringToElement("home")) </label>
      <ul> <li> <Link href="/" label="Home" /> </li> </ul>
      <label> (ReasonReact.stringToElement("pages")) </label>
      <ul>
        <li> <Link href="/page1" label="Page1" /> </li>
        <li> <Link href="/page2" label="Page2" /> </li>
        <li> <Link href="/page3" label="Page3" /> </li>
      </ul>
    </nav>
    <main>
      (
        switch route {
        | Home => <Home />
        | Page1 => <Page1 />
        | Page2 => <Page2 />
        | Page3 => <Page3 />
        }
      )
    </main>
  </div>;
}