Went and started tested Nitrome's back catalogue in Ruffle, after finding a heavy amount were unruffled. Seems I've discovered a hotbed of issues.
All games tested on Firefox, using Ruffle 0.1.0 nightly 2025-06-12.
Game freezes on a white screen after pressing "Play".
Game freezes at the Nitrome logo, and crashes upon clicking. [crash log sent]
Game freezes at the Nitrome logo, and crashes upon clicking, like RT:NY.
Menu text fails to render. Help screen rapidly cycles through all available images until you click either arrow. Couldn't start a game either, as all the levels were locked.
Similar issues - issues with rendering menu text. Game isn't working, either - starting a game gets me a white screen, with a flashing HUD.
White screen.
Menu text (outside the main menu) fails to render. Game freezes upon starting a level.
Game freezes upon clicking any menu option other than "Start". Level select fails to render text, and the main game is near-white due to a broken transition.
Text rendering issues in the menu. Game cannot start thanks to all levels being locked.
Game freezes at Nitrome logo, but doesn't crash upon clicking.
Game freezes at Nitrome logo, and crashes upon clicking. Cause appears identical to RT:NY and Test Subject Blue.
Game refuses to start, stating an "error loading the game":

Played and finished the first two levels without issue. [enable ruffle]
Game freezes at the preloader. Clicking "Play" in the context menu allows the Nitrome logo to play, before freezing again. Clicking "Play" again advances to the main menu, which bugs out severely before returning to the preloader.
Game freezes at the preloader. Clicking "Play" in the context menu allows the Nitrome logo to play, before freezing again. Clicking "Play" again advances to the main menu, which bugs out severely before returning to the preloader. [disable ruffle]
Game menu functions. Playing Level 1 was impossible - Chiseller is unable to move, and the planet fails to render. Trying to restart caused an infinite loop. [disable ruffle]
Menu has text rendering issues. Game freezes upon starting a level in Story Mode. [disable ruffle]
Game fails to start, looping at the Nitrome logo.
Game refused to start.
Game refused to start.
I stopped testing after J-J-Jump - seemed redundant to keep testing - but I did find two HTML5 games broken in both Firefox and Brave:
Both games give a black screen in Brave/Chromium, whilst Firefox refuses to load them due to being HTTP-only. Manually loading them anyway led to a black screen as well.