OK. If you are still with me we can start shading other shapes.Follow the tips written above and get the rectangular marquee tool and do it just like a circle till the blending options, hope you got it. Than you going to have something like the picture below: You can still play with the settings.But if you want to have the rectangle without sharp edges, it is quite easy just when you are about to make a rectangle go to Select/ Modify/ Smooth. I used 7 pixels. And follow the steps that were used for a green rectangle above. And got this:Hope that the tutorial was not so difficult to understand, just play with the settings. And here are my other shaded shapes: