The same is probably true for any other game. I don't think there are any where the input goes to some hidden text field or something like that.

That extension should have an option for disabling shortcuts for the current tab.

Press i in Vimium, ctrl-z in Pentadactyl, or shift+esc in Vimperator, and they will pass everything except esc (shift+esc in vimperator) to the page.

Thanks! I did read vimium's readme years ago, but in the meantime I had totally forgotten about insert mode.

I use Firefox with "Search for text when I start typing" enabled. Some games break due to this option, but this game is okay for me.

...as one might expect?