Features included:

• Consistent default styles across browsers
• Proper box-sizing: border-box
• Responsive images
• Accessibility improvements

<!-- Display Classes -->
<div class="uk-visible">Visible</div>
<div class="uk-hidden">Hidden</div>
<div class="uk-invisible">Invisible but occupies space</div>

<!-- Responsive Display -->
<div class="uk-visible@s">Visible on small+</div>
<div class="uk-hidden@m">Hidden on medium+</div>
<div class="uk-visible@l">Visible on large+</div>
<div class="uk-visible@xl">Visible on xlarge+</div>

<!-- Flex Container -->
<div class="uk-flex">
  <div>Flex item 1</div>
  <div>Flex item 2</div>
</div>

<!-- Flex Direction -->
<div class="uk-flex uk-flex-row">Row (default)</div>
<div class="uk-flex uk-flex-row-reverse">Row Reverse</div>
<div class="uk-flex uk-flex-column">Column</div>
<div class="uk-flex uk-flex-column-reverse">Column Reverse</div>

<!-- Justify Content -->
<div class="uk-flex uk-flex-left">Left</div>
<div class="uk-flex uk-flex-center">Center</div>
<div class="uk-flex uk-flex-right">Right</div>
<div class="uk-flex uk-flex-between">Between</div>
<div class="uk-flex uk-flex-around">Around</div>

<!-- Align Items -->
<div class="uk-flex uk-flex-top">Top</div>
<div class="uk-flex uk-flex-middle">Middle</div>
<div class="uk-flex uk-flex-bottom">Bottom</div>
<div class="uk-flex uk-flex-stretch">Stretch</div>

<!-- Margin -->
<div class="uk-margin">Margin all sides</div>
<div class="uk-margin-top">Margin top</div>
<div class="uk-margin-bottom">Margin bottom</div>
<div class="uk-margin-left">Margin left</div>
<div class="uk-margin-right">Margin right</div>
<div class="uk-margin-remove">Remove margin</div>

<!-- Padding -->
<div class="uk-padding">Padding all sides</div>
<div class="uk-padding-small">Small padding</div>
<div class="uk-padding-large">Large padding</div>
<div class="uk-padding-remove">Remove padding</div>

<!-- Spacing Sizes -->
<div class="uk-margin-small">Small (5px)</div>
<div class="uk-margin">Medium (15px)</div>
<div class="uk-margin-medium">Medium (30px)</div>
<div class="uk-margin-large">Large (40px)</div>
<div class="uk-margin-xlarge">X-Large (70px)</div>

<!-- Borders -->
<div class="uk-border">Border all sides</div>
<div class="uk-border-top">Border top</div>
<div class="uk-border-bottom">Border bottom</div>
<div class="uk-border-left">Border left</div>
<div class="uk-border-right">Border right</div>

<!-- Border Styles -->
<div class="uk-border-dashed">Dashed border</div>
<div class="uk-border-rounded">Rounded corners</div>
<div class="uk-border-circle">Circle border</div>
<div class="uk-border-pill">Pill shape</div>

<!-- Border Colors -->
<div class="uk-border-primary">Primary border</div>
<div class="uk-border-secondary">Secondary border</div>
<div class="uk-border-muted">Muted border</div>

<!-- Basic Grid -->
<div class="uk-grid-small uk-child-width-1-2@s uk-child-width-1-3@m" uk-grid>
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

<!-- Grid with Gutter -->
<div class="uk-grid-divider uk-child-width-1-3" uk-grid>
  <div>Item with divider</div>
  <div>Item with divider</div>
  <div>Item with divider</div>
</div>

<!-- Nested Grid -->
<div class="uk-grid-small" uk-grid>
  <div class="uk-width-2-3">
    <div class="uk-grid-small" uk-grid>
      <div class="uk-width-1-2">Nested 1</div>
      <div class="uk-width-1-2">Nested 2</div>
    </div>
  </div>
  <div class="uk-width-1-3">Sidebar</div>
</div>