Bulma class: .hero.is-halfheight

<section class="hero is-primary is-halfheight">
  <div class="hero-body">
    <div class="container">
      <h1 class="title">
        Primary title
      </h1>
      <h2 class="subtitle">
        Primary subtitle
      </h2>
    </div>
  </div>
</section>

Preview

Primary title

Primary subtitle

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