With support for Adobe Flash Player ending on 31/12/2020, you might be wondering what's going to happen with speedrunning not only This Is The Only Level, but also other flash games. The answer? nothing really, all thanks to Flashpoint, it is a web games preservation project with a large built in archive of all your favorite flash games. You can download it from the link below:

https://bluemaxima.org/flashpoint/

https://www.adobe.com/support/flashplayer/debug_downloads.html there is a link to download the standalone flash player if you want to, and here is the swf link in the internet archive: https://archive.org/details/flash_thisistheonlylevel

Everything is also in the Resources page here: https://www.speedrun.com/titol1/resources