Three years ago, an independent game designer decided that turning crayon scribbles into physics-based puzzling gameplay was a mighty fine idea. Two years ago, that idea won him the Independent Games Festival’s prestigious grand prize. And one year ago, he released the game for public consumption at a $20 price point.

That brings us to today. Today, in honor of its birthday, creator Petri Purho has decided to let you have a copy of Crayon Physics Deluxe — through January 15 — for whatever you’re willing to pay.

Assuming you have a PayPal account, simply click this link, choose your donation value (I chose $5) and an email will immediately appear in your inbox, with a link to the full game download.

As experimental game pricing models go, the pay-what-you-want idea isn’t new; fellow IGF finalist 2D Boy pioneered the scheme last October with their physics-puzzler World of Goo. In their analysis of the sale’s results, 2D Boy noted that donations of less than 30 cents don’t really help much, as PayPal takes it all in transaction fees.

[Source: Kloonigames via @PetriPurho]