fed

Hi guys, I have a wordpress website and I'd like to use the header in a custom HTML page in which I complete the body and footer with HTML5, CSS and Javascript. What's my best option: do I create a PHP file which includes the HTML (option 1) or do I create a HTML file which includes the reference to header.php (option 2)? The purpose is that I can point directly to this page (e.g. mypage.html) from both a wp and non-wp website. As such, how would the code look like so that it "recognizes/finds" header.php and also links to the corresponding CSS and JS files which is required to complete the body and footer? Thanks for helping me out. Fed