I want to create a simple game in HTML5/JS and I don\'t want the user to run any webserver or to have to connect to a website. (just an HTML page)
But it looks like
I believe that this is your answer: How to open a local disk file with Javascript?
In short, you are looking something like this:
HTML5 allows you to load files which are stored locally on computer, but you cannot select it. User must select file which he/she wants to be loaded.
Just imagine what would happen when developers (or better spoken, hackers) would have access to everyones local data...