To celebrate the game's first birthday, indie developer 2D Boy is encouraging fans to purchase the PC, OS X, and Linux editions of World of Goo for whatever they think the game is worth. And if you're not sure how to gauge its price, you can always grab the IGF multi-award winner's demo from the studio's site (once it's a bit more stable, that is).

Whether you think the game should cost a single penny or $500 (it's typically $20), you can grab World of Goo for whatever amount you come up with starting today until October 19th. The WiiWare edition, unfortunately, remains priced at 1500 Nintendo points ($15).

2D Boy also announced that a port of the title to iPhone and iPod Touch is in the work. "It’s not done and we don’t have a release date yet," says co-founder Kyle Gabler, according to a report from Casualgaming.biz. We have it running well on the iPhone 3GS, and with a little luck we hope to get it running smoothly on the 3G as well. Hopefully more news on this soon.