How to Perfectly Center a Triangular Element Horizontally During Window Resizing?

Maintaining Horizontal Centering of an Element During Window Resizing

Problem:
Centering an element horizontally through CSS can be tricky when the window is resized, particularly for elements with a triangular shape.

Addressing the Issue:
To ensure that an element remains horizontally centered regardless of window size, it's essential to use the correct CSS property and understand how element positioning works. While setting left: 50% may seem intuitive, it actually positions the element based on its left edge, not the center.

Solution: Transform and Translate
To achieve true horizontal centering, it's common to use the transform: translate() property. This property instructs the element to shift itself back by a specified percentage of its width, effectively centering it on the desired axis.

Applying Transform to Existing Code
In the provided code, the triangle element is initially positioned with left: 48%, which places it close to the center but incorrectly. To adjust this, we can use the transform: translate(-50%, 0) rule to shift the element back by 50% of its width, ensuring it's perfectly centered.

Chaining Transformations
However, the provided code also includes a transform: rotate(45deg) property, which is applied before transform: translate(-50%, 0). This causes the transform: translate() rule to be ignored due to the CSS cascade.

To account for this, we can combine both transformations using the transform property's ability to chain functions. The final CSS rule for the triangle element will be:

.container::before {
    top: -33px;
    left: 50%;
    transform: translate(-50%, 0) rotate(45deg);
    position: absolute;
    border: solid #C2E1F5;
    border-width: 4px 0 0 4px;
    background: #88B7D5;
    content: '';
    width: 56px;
    height: 56px;
}

By chaining the transform functions in this order (translate() first, followed by rotate()), we ensure that the element is first shifted back by 50% of its width and then rotated by 45 degrees. This ensures that the triangle remains horizontally centered even when the window is resized.

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