As far as I know, you can't download it to play it. It has to be played in the browser and from a server. 1.0 is out and is the available on the main page.
Thanks a lot, as i say, i download 0.5, and this it WORKS offline (for that i want to download). So i was thinking the others can be use. Seems i was thinking the download its for play offline, but seems its only for work or something.
Its good to know that, thanks to you i just focus to play it here.