Interesting... Do you mind telling me which browser and OS you are using? And, is there a particular location that the problem happened?
I have tested it with different browsers in Windows on different laptops . My laptop does not even have a separate GPU, and it plays at high 50 fps (except the Kaiju's in the City, which is mid to high 40 fps). It does chokes for a second before transitioning to a new scene/room because of the scene loading.
Thanks for playing my game.