Thanks for the comment, I guess I tried my best, Besides, I'm kind of not good at drawing pixelart.

I wish i can look at the best tutorial that how to draw pixelarts.

Geez, I wish i could practice more if i can... ^ ^;

Allow me to confuse the issue further by complaining that this ISN'T a perfect circle-there's a notch in each of the sides making it uneven. Most obvious on the bottom right edge. Also the lighting doesn't quite make sense, the shadows in and around the hair are inconsistent with the light source, and then the feet have it backwards. It's good that you aren't pillow shading, but it might help to draw in a light source to remind yourself to keep it consistent.

Early days yet, keep practising!

the colors are kinda jarring; the orange is very (probably too) saturated, at least to me. the pallete could also use a lot more contrast in general, it's hard to tell there's any shading at all and so it looks really flat. more pronounced shading could add to the whole "ball" thing, cus right now its basically a circle with some doodads.

also, unless you were specifically trying, i'd avoid shapes being so "perfect"-- a little irregularity can give a character a lot more emotion, attitude, etc.