How to Make a 'Raise the Curtains” Effect in CSS

This CSS effect, which I call "Raise the Curtains," creates a visually striking transition on scroll. The background shifts from dark to light, while the sticky content above transitions from light to dark.

Here's how it looks in a real-world application: [link to example - replace with actual link if available]

Ready to learn how to create this effect? Let's dive into a simple HTML and CSS implementation.

HTML Structure

For clarity, we'll use a simplified version:

<div class="curtain">
  <div class="invert">
    <h2 id="Section-Title">Section Title</h2>
  </div>
</div>

This uses a .curtain container for the background effect, an .invert child element for the sticky content, and an <h2></h2> for the heading.

CSS Variables

We'll define CSS variables for easy customization:

:root {
  --minh: 98vh;
  --color1: wheat;
  --color2: midnightblue;
}

These variables control the container height (--minh), light color (--color1), and dark color (--color2).

Creating the Curtain Effect

The .curtain element uses a linear gradient for the background split and min-height for extra bottom space:

.curtain {
  background-image: linear-gradient(to bottom, var(--color2) 50%, var(--color1) 50%);
}

.curtain::after {
  content: "";
  display: block;
  min-height: var(--minh);
}

The ::after pseudo-element creates the illusion of extra space, ensuring the sticky content remains within the container.

Implementing Sticky Content

The .invert class styles the sticky content:

.invert {
  position: sticky;
  top: 20px;
  mix-blend-mode: difference;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: var(--minh);
}

h2 {
  color: var(--color1);
}

position: sticky and top create the sticky effect. mix-blend-mode: difference blends the content color with the background gradient, creating the inverse effect. Flexbox centers the content.

The mix-blend-mode: difference creates an inversion effect. For a visual explanation of mix-blend-mode values, see this CSS-Tricks Almanac demo: [link to CSS-Tricks demo - replace with actual link if available].

Demo and Considerations

A live demo showcasing the effect can be found here: [link to demo - replace with actual link if available]

Important Notes:

• Images within the sticky content might not render well with color inversion. Consider using SVGs or transparent PNGs.
• mix-blend-mode: difference doesn't work well with certain properties like transform on the container.

This technique offers a clean, browser-compatible solution for creating a visually appealing "Raise the Curtains" effect using only HTML and CSS. Let me know in the comments how you'd use this effect!

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