Flash is dead etc etc. For Kongregate users who still want to play SM, I put together firefox portable v70 and flash player 32 in a zip file (since this whole thing is like 480mb uncompressed). Just extract the "FirefoxPortable" folder to wherever and run Firefox.
Disclaimer: This version isn't getting security updates, ever, so only use this to run SM.
https://www.mediafire.com/file/712uj45c5b3zgxc/FirefoxPortable.zip/file
If you get the EOL page: Uninstall flash player via Adobe's official uninstaller then extract the firefox folder again
If SM is slow: type about:preferences#privacy into the URL bar and set tracking protection to enhanced (this blocks some ads)
Make sure supernova player isn't installed, and click "more options" if it shows you this prompt
(not this specific part of the prompt though, if it asks to enable flash then enable it)