[not2b]

You can guess it in one try by carefully reading the code. There is no server that knows the correct answer. The client already knows, based on the date. That is why you can only play once per day.

[ska]

That's not really guessing though, is it?

[echeese]

Where's the challenge in that?

[klyrs]

Reading the minified code, probably.

[rkimb]

It's a giant array, tough to miss

[gojomo]

Thanks, Captain Kirk. You get a commendation for knowing how to 'View Source'.

[guipsp]

Yes, but there's no fun in that

[zamadatix]

As already explained by carefully reading the opening of the post.