i think i found a nice solution for the key problem (gamejs used to swollow all keypress on the page, so the player couldn't even fill out a form).
now, the keys are only suppressed if the display has focus. you have to click the canvas to focus it & initially it's focused. so it's a bit like flash, which i think is
good.
and i added gamejs.display(res, gamejs.display.DISABLE_SMOOTHING)
<
http://docs.gamejs.org/gamejs/display/#setMode>
have fun
simon