You know what is funny...
I wrote to them about a day or two after its initial release and told them I just heard about the game and could I get it for the preorder price. I was told, no. As I recall it was only $5.00 less than the full price (I could be wrong there).
Now, I can buy it for a whole lot less since I had no intention to buy it at full price. Funny how things work out if you give it enough time.

Already got my copy. Couldn't donate much though, and I feel bad for that. :(

I must admit I was so looking forward to this game before it came out, but after trying the demo, I decided not to buy it after all. I thought the level design was poor, to say the least. It's a pity, because the concept is brilliant. I think he could have done a lot more with it, though. Still, with this deal I might get it after all, just to show support.

I don't follow...what's wrong with the serial being a *.txt?

Heard about it a while ago... now that it's "pay what you want", I guess it's finally time to try it out.

I got it a while back in the Steam indie bundle as well and its a neat little game but thats all. I quickly got bored of it.

Looks like it has a nice concept...
Oh, Paypal only. Damn. :(

It seems kind of silly to put it into an attachment instead of into the email body.

Or credit card, if you find the tiny link. 2D Boy gave directions for those who got confused when trying to buy World of Goo, same directions apply here as well.

I don't get the same thing as on the screenshot. :/
But still, my country is not listed on Paypal.

Just curious, but what do you use for email? I know some programs/online services render specific types of signatures as txt files.
I know that when the email is sent to Gmail it shouldn't have any attachments, as mine didn't.

I use AOL mail (laugh all you want). Signatures are rendered normally as little grey bits of text on the bottom of the email.

Whatever did big corporations do to you?

AOL still exist? D: I haven't seen or heard of any sign of them for many years now.

Oh yeah, don't get me wrong. The signatures still display normally in the email, but are actually sent as attachments. Google groups recently didn't something to the way they send signatures which cause some email services/clients to receive them as attachments, so it's likely that something similar is happening in your case. Did you actually open the txt file?
Mind you, I've also received emails from clients in the past where the entire email arrives as a text attachment, html attachment as well as being rendered as a normal email.