@Dungeonation pointed out that Cathode Raybots can load levels in Ruffle now. Here's a test link if you're curious!
A few notes: You'll get to a mode select screen that will be completely blank because blend modes aren't supported yet. Click the left side of the screen to go to the level select menu. You'll then be able to select a level and it will successfully load, although the level layout itself won't be visible because it requires Cache as Bitmap functionality. Ruffle has been making progress with bitmaps and blend modes so I'm looking forward to these working in the future!
For now, it's cool to see how well the level actually runs; it never felt that smooth in the Flash Player. Cathode Raybots was a big project for me where I was trying to expand on my abilities. It has a level editor, a gameplay recorder for enemy patterns and a drawing tool, all capable of saving user creations to NG. It was a game intended to flex our content sharing API, which sadly released as Flash was on its way out. @PsychoGoldfish might eventually introduce a similar system via Newgrounds.io for HTML5 games; he's working on cloud saves at the moment.
With NG and Flash in decline at the time of Cathode Raybots' launch in 2013, I felt like it never got to live up to its potential. At least people will be able to keep playing it, thanks to Ruffle!
Dungeonation
Cathode Raybots IS the Newgrounds API to me, rising like a phoenix currently in its IO iteration and in Ruffle. So awesome to see! I should also point out from testing that uploading levels and faces works but with bitmap stuff still a work in progress there won’t be a thumbnail with it.