The flex-wrap property in CSS is used in a flexbox layout. It controls whether the flex items should wrap onto multiple lines when there's not enough space in the container.

Here are the possible values for flex-wrap:

• nowrap: This is the default setting. The flex items will stay on one line and will not wrap.
• wrap: The flex items will wrap onto the next line if there isn't enough space.
• wrap-reverse: The flex items will wrap onto the next line, but in the reverse order.

Here's a simple example to illustrate how to use flex-wrap:

css
 
 
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.container {
  display: flex;
  flex-wrap: wrap; /* Allows items to wrap onto the next line */
}

.item {
  width: 100px;
  height: 100px;
  margin: 10px;
  background-color: lightblue;
}

And here’s how you can apply it in HTML:

html
 
 
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<div class="container">
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
</div>

In this example, if the container is too small to fit all the .item boxes in one row, they will wrap onto the next line. You can play around with the container's width to see how it behaves!

To create a responsive image grid, you can use CSS grid or flexbox. By defining specific rules such as widths and heights or by using media queries, these techniques will enable your image grids to maintain their proportions while adjusting to different screen sizes.

Here is an example code for a responsive image grid created using CSS grid:

css
 
 
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.image-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  grid-gap: 10px;
}

.image-grid img {
  width: 100%;
  height: auto;
}

In this code, auto-fit will generate however many columns will fit into the container, with a minimum size of 250px and a maximum of 1fr. The grid-gap property specifies the spacing between each grid item. In the case of the img tag, setting the width to 100% and height to auto will ensure that the image aspect ratios will be maintained while scaling.

Another approach would be to use flexbox like this:

css
 
 
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.image-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
}

.image-grid img {
  width: calc(33.33% - 10px);
  margin-bottom: 10px;
}

@media (max-width: 768px) {
  .image-grid img {
    width: calc(50% - 10px);
  }
}

@media (max-width: 480px) {
  .image-grid img {
    width: 100%;
  }
}

In this code, we can use the flex-wrap property to wrap items into more rows than a single line as the container shrinks. justify-content: space-between ensures that the images will be distributed equally between the container. The media queries specify what will occur when the screen-size is a certain width - this is helpful when trying to optimize for mobile and tablet devices.

I hope that helps! For more information and other techniques, you can check out this article.