2D Boy is celebrating the first birthday of World of Goo in two ways - firstly by announcing a new sale and secondly by announcing that an iPhone version of the game is on the way.

Firstly though; if you don't know what World of Goo is then it's a physics-based puzzler from small indie studio 2D Boy. It's awesome. You should buy it, especially if you're one of those evil people who pirated the game.

Interestingly, 2D Boy is letting customers pay whatever they want for the game if they buy it before October 16th too, though there is a demo on offer if you want to try before you buy.

"If you played and liked the game but hadn't yet paid for it, this is your chance at redemption," said 2D Boy on the official blog, commenting on the rampant piracy that has plagued the game.

2D Boy has also followed up the sale with the announcement that the game, which is already available on Mac, Linux, PC and WiiWare, is also going to be coming to the iPhone in the near future. There's no feature set or release date yet announced, but it apparently runs well on a 3GS already and is being optimised for older handsets.

Oh, and if you want some more free World of Goo goodies then don't forget that you can download that spectacular soundtrack for free too.

Picking up a copy? Let us know in the forums.