There's at least one medal (and possibly two) you can't get except on Chrome. I had played the entire thing through on Firefox and was short two medals. Played on Chrome sometime later and surprise surprise one very easy medal right at the start for an ability that literally doesn't work under Firefox.
Then sometime not too long after that I unlocked the final medal I was missing, which I'm not sure what the reqs were for that one, but wouldn't surprise me if it required using that Chrome-only ability.
If your game only correctly works on one of Firefox/Chrome, you need to fix it so it at least works correctly on *both* browsers.
Also this is a very laggy RAM-hog game as well.