it's alright. the shadow on the bottom-right of the sphere makes no sense however, as the light-source is on the top-right of the screen. also, it's not necessary to add that many shading colors (keep it below 3 at least). and lastly, the sphere itself can be rounded out a bit more nicely; there appears to be "corners" at its, well, corners. you've done pretty nicely though :3 <3