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<!DOCTYPE html>
<html>
<head>
<style>
#myDIV {
  background-color:lightblue;
  width: 100%;
  min-block-size: 30px;
  animation: mymove 5s infinite;
}
@keyframes mymove {
  50% {min-block-size: 150px;}
}
</style>
</head>
<body>
<h1>Animation of min-block-size</h1>
<p>Gradually change the min-block-size property from 30px to 150px, and back to 30px. The limited content keeps the box from getting smaller in the block direction:<p>
<div id="myDIV">
  <p>This is my DIV element.</p>
  <p>This is just some more text to fill the box.</p>
  <p>This is just some more text to fill the box.</p>
</div>
</body>
</html>