Cool game, the screen went solid black after I beat the "ALMOST" level...
Oh no, sorry to hear that. I just replayed it in the browser and that didn't happen to me so I'm not sure what the issue is, but after that is pretty much just the credits.
I edited the files so that the level select screen includes an option to go directly to the ending. So, if you replay level 5 and get a black screen again, you can refresh your browser and go to the level select screen and choose "End" and it'll take you directly to the last scene and then play the credits.