Complete Code For Gradually Change Border Top Size Using CSS Animation.
<!DOCTYPE html> <html> <head> <title>How Gradually Change Border Top Size Using CSS Animation</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css"/> </head> <style> * { box-sizing: border-box; } body { background-color: #777891; } #myDIV { width: 300px; height: 200px; border: 1px solid black; animation: mymove 5s infinite; } @keyframes mymove { 20% {border-top: 15px solid lightblue;} 50% {border-top: 25px solid lightgreen;} 100% {border-top: 55px solid lightpink;} } </style> <body> <br/><br/> <div class="container"> <br> <div class="text-center"> <h1 id="color" style="color: white;">Gradually Change Border Top Size Using CSS Animation</h1> </div> <div class="well"> <div id="myDIV"></div> </div> </div> </body> </html>