CSS: how to style on character height versus line height

Bear with me here, but assuming this code:

<style>
  span {
    color: black;
    background-color: black;
  }
</style>
<span>Hello world</span>

Hello world

Gives a result that looks like this:

███████████

Is it possible to apply style to just the letter height, versus the font/line height? In effect ending up with something that looks like this:

█▄██▄ ▄▄▄██