Wow you always seem to find unknown bugs haha! Not sure if that is to do with Mac or not! There are definitely other rounds. Did you use the delete key before clearing the bricks or just after it didnt seem to progress? Considering that doesnt look like an HTML5 crash for GMS2 (the screen would just turn black) it looks like it just didnt progress like it should have.
In the end you didnt miss much except for being able to duplicate the 'ball' on the final round in order to clear things faster (well and also the story I guess which is a big thing for this round O.o). I had so much I wanted to include but so little time in the end, even with the 2 weeks haha. I still have yet to leave myself ample time for polish with jams and things like your font suggestion probably would have come in to play. I tend to pick something to try that I've never done when I do jams to see if I can do it and this time it was converting strings to breakout blocks haha. Thanks for checking it out!