CSS Length Units

Percentage

We use percentages to specify lengths when we want to size on item relative to its parent element.

Code example

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<style>
#blue-box {
  width: 250px;
  height: 250px;
  background-color: blue,
  color: white;
}

#red-box {
  width: 75%;
  height: 50%;
  background-color: red,
  color: black;
}
</style>

<div id="blue-box">
  I am a blue box with a width of 250px and a height
  of 250px
  <div id="red-box">
    I am a red box with a width of 75% and a height
    of 50% of inside the blue box
  </div>
</div>

which produces

I am a blue box with a width of 250px and a height of 250px

I am a red box with a width of 75% and a height of 50% inside the blue box

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85%

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85%

<div class="art">
  <h2>Inception</h2>
  <div class="level">
    <div class="level">
      <div class="level">
        <div class="level">
          <div class="level">
            <div class="level">
              <div class="level">
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  </div>
</div>

.art {
  width: 461px;
  height: 284px;
  background-color: #e56408;
  position: relative;
}

.level {
  background-color: inherit;
  filter: brightness(75%);
}

h2 {
  margin: 0;
  padding: 0;
  color: white;
  text-transform: uppercase;
  writing-mode: vertical-rl;
  text-orientation: upright;
  position: absolute;
  right: 10px;
  top: 20px;
}