Really mesmerizing! I've actually been watching Hypermasher from time to time since it was also submitted here [1]. I like the improvements that you've made, the interface is certainly nicer, and your codebase appears to be more concise. Hypermasher could run without Flash (barring the music), but Hyperlax refuses to start without it, however that's just a nitpick (though you might be surprised at the number of people who have flash disabled by default these days.)
Regarding the flash issue, you're right, I'm noticing this too. Completely didn't think about that. The "let's go" button waits for the sound to finish loading, but if it never does, you can't start it :/.
I'll look into this, hopefully not too many people are affected.
[1]: https://news.ycombinator.com/item?id=8309848