I want you to act as a web developer and please write some code for me to create a progress bar for a website.

I want you to act as a web developer and please write some code for me to create a progress bar for a website.
Stylistic approach:
The design features rounded corners, with both ends forming semi-circles (border-radius: 100px or a similar value).
The progress bar fill area should have a gradient background to add a modern touch.
Dynamic animation:
When the progress value changes, the width’s variation must be a smooth transition animation (using transition: width 0.3s ease), rather than a sudden jump.