I can go try it in Firefox. I haven't had success with Chrome or Safari (I'm a Mac user, for what it's worth - it seems like this may in fact be a MacOS issue).
Viewing post in Watch out for the asteroids! jam comments
Strange why it works in Firefox. I tried running the game in Safari on my Mac but I couldn't reproduce the "UnityLoader is undefined" error, safari had some issues rendering the background but otherwise it worked. Are you using any extensions in your browser that could interfere with loading javascript?