Rarely should there ever be shadow without highlight. In other words you need a long bright highlight on the right side of the pill's surface to really emulate lighting well. Try 'er.
I like the dithering on the shadow side very much.
I agree with Larwick in one respect: you shouldn't antialias horizontal, vertical, or 1:1 diagonal lines that go through the centre of every pixel that they cross.
AA practice? Nonnonononono. Why did you AA the outside, not the inside? Don't AA 45 degree angles. Neat character. He looks a bit flat though, probably due to the lack of colours used to define depth. Also the line splitting the two colours is a bit wonky. I think you should work on it some more, will turn out pretty cool.
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Rarely should there ever be shadow without highlight. In other words you need a long bright highlight on the right side of the pill's surface to really emulate lighting well. Try 'er.