<div class="card">
  <h3 class="card__title">Duis aute irure dolor</h3>
  
  <p class="card__text">Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim.</p>
  
  <p class="card__text">Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
</div>

HTML {
  font-size: 14px;
}

BODY {
  font-size: calc(1rem + .5vw);  
  line-height: calc(1.2rem + .5vw);  
}

.card {
  min-width: 300px;
  max-width: 400px;
  padding: 1rem;
  box-sizing: border-box;
  border: 1px solid #DDD;
  
  &__title {
    margin-top: 0;
    margin-bottom: 1rem;
    font-size: 1.4;
  }
  
  &__text:last-child {
    margin-bottom: 0;
  }
}

// Helpers
BODY {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0 1rem;
  font-family: Trebuchet MS, Arial, sans-serif;
  line-height: 1.3;
}