Long long time ago, the game used a terrible game engine called godot that could barely run on web, sound didn't work properly, big build sizes, crashes and memory leaks on apple devices, and barely got over 30fps. Standalone builds (mobile and desktop) worked fine and was provided for a small donation. Since the game primarily targets the web, I ported it to html/js/css and got rid of the downloadable versions since it was cumbersome to update two separate versions and it didn't feel fair packaging a web page as an app or an exe. So, no, you can no longer download it. Sorry!
Erm, actually, if you download the ITCH.IO app, then input this web address: https://cyfo.itch.io/duck-duck-clicker into the bar IN THE APP, then click download. And BOOM, there you go