How and Where to modify source of index.html and player.css

Problem: Default CSS
Hi, each time I export in HTML5, Active Presenter overwrite my index.html and my player.css files which I had customized. Can I modify directly the source of those files so when I export Active presenter use my modified version on index and css?

ActivePresenter Version: 6.0.3

OS: Win7 IE11

Notes:

Ok, I found my answer : https://atomisystems.com/community/11175/where-does-the-demo-png-image-come-from?show=11181#c11181