HTML doesn't have a way of expressing logic, like conditionals and loops. Svelte does.

To conditionally render some markup, we wrap it in an if block:

{#if user.loggedIn}
  <button on:click={toggle}>
    Log out
  </button>
{/if}

{#if !user.loggedIn}
  <button on:click={toggle}>
    Log in
  </button>
{/if}

Try it — update the component, and click on the buttons.