So As of a lot of you may know flash is no longer available for Browsers, So that means that OBA (One Button Arthur) will no longer be playable on web browsers since it's a flash game. But That doesn't mean that playing the game is not possible anymore

First step is to go to this site, and download SuperNova Player from there https://www.bubblebox.com/play/1884/one-button-arthur.htm

After It's downloaded Click play on the site and it should open on the launcher

Note: You May have some issues with launching the game at first but closing and opening the launcher should fix that.