Why Is My Z-Index Not Working When Using Transform or Translate?

Z-Index Not Working: Understanding the Issue

The z-index property is a widely used CSS property that controls the order in which elements are layered in a webpage. However, sometimes it seems to malfunction, leaving elements stubbornly stacked in the wrong sequence. This issue can be particularly vexing when dealing with complex layouts involving multiple layers.

Understanding the Z-Index Issues:

One specific example where z-index appears ineffective is when attempting to position an element behind a circle. Despite assigning a lower z-index value to the element, it remains persistently visible on top of the circle. The reason behind this lies in the way transform and translate properties interact with z-index.

Transform and Translate's Impact:

When using transform or translate properties to move elements, they create a separate stacking context. This separate context places the elements outside the normal flow of the document and renders the z-index property ineffective. As a result, elements within this separate context cannot be positioned correctly using z-index alone.

Solution: Resolving the Z-Index Dilemma:

To resolve this issue, you can replace the transform or translate properties with top and left properties. By setting specific values for top and left, you can manually position the element within the regular stacking context and regain control over its placement using z-index.

Modified Example:

The following modified code snippet demonstrates how replacing transform with top and left allows you to correctly position the element behind the circle:

<code class="css">#background #mainplanet:before, #background #mainplanet:after {
  ...
  transform: none; /* Remove the transform property */
  top: 10px; /* Set the top position */
  left: -80px; /* Set the left position */
  ...
}</code>

By making these changes, you can now use z-index to effectively control the layering of elements and achieve the desired visual hierarchy.

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