UPDATE: Can log in now. Cleared browser cookies, but have no idea if that's a coincidence or not.
I seem to have hit some kind of bug signing up:
1. Filled out signup form, hit enter.
> Page reloaded, sign-up form empty. No other feedback.
2. Filled out signup form again, hit enter.
> Told username and email address taken.
3. Check email.
> no new email.
4. Filled out login form using info entered in step 1.
> Page reloaded, not logged in.
Update 5 min later: Maybe not. I logged in and while playing First Steps is listed in "Stuff You Can Do", clicking a level from Level Controls is instead throwing errors in the console.
I'm assuming this is not part of the game.
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It looks like email invites went out about the same time as the HN post, but it seems to be good now.
+1 exactly the same problem. Maybe it is because of the high number of requests. I'm astonished that the site is still up despite being #1 on the front page. EDIT: Yup, clearing cookies solves this
Try clearing cookies for the site and try logging back in.