Oh no! I've been trying to recreate this bug but I can't. I even downloaded Opera browser and it works fine for me. But if it helps, I did just upload a downloadable version of the game for Windows -- maybe that would help?
If not, I also just uploaded the game on Newgrounds: https://www.newgrounds.com/portal/view/1025458
Regardless, apologies! I wish I could recreate it to fix it, but thank you for pointing it out! You inspired me to at least offer alternative ways to play it. Eventually a downloadable demo will also be on Steam too.