When you create an EPUB file, you can specify whether the content within it is reflowable or not. If you want the content to be reflowable, you need to add the following code to the file:
<meta name="viewport" content="width=device-width, initial-scale=1.0">
This code tells the EPUB reader that the content within the file is intended to be displayed on a screen of a specific width (in this case, the width of the device), and that the content should be scaled up or down accordingly.
