Water Chicken

Thanks! Just what I was looking for!

Hi, I'm wondering how I could make like a spiral/circle gradient(not sure if that's correct...)? Say you have a circle with 1 quarter cut out(bottom right)like this image: How would I make a white to black gradient following the red path from point A to B? I'm not sure how I would do this. Any help would be appreciated. Thanks in advance! P.S: I'm needing this for a game I'm making in Unity3D, it's sorta like Jak and Daxter's eco meter.