Hello. I published and tested using Firefox in Windows. It is working for me, but I'm noticing that in some times it takes some tries to detect that key press particular. I think the problem could be the iFrame loses the focus or the framerate in the loop waiting for the key press is too fast and discards the event.
In the meantime I'm able to update the project you could try to press the key several time in different speeds and clicking the screen making sure it has the focus. Fullscreen mode could help, but I'm noticing I forgot to add the option.
Thank you.