http://www.neogaf.com/forum/showthread.php?t=460186What is Tsilon? Do I have to complete this game to get the Halo code?
If you need an invite to the site then PM me the email address you want to sign up with and I'll send you one. I have no idea if they've fixed the invite system or if invites are sent in a reasonable timeframe. Otherwise you have to figure out how to join and I have no idea on that any more.
Oh yeah, once you do join then start entering the daily answers (almost always in spoiler tags so they're easy to spot) from the GAF thread starting on page 70 until now and you'll fly through the first bunch of levels.