"Are you still there?"

[Alex IDV]

Avoid using black, especially on the inside of a sprite - it kind of eats the whole sprite up. The turret is kinda deformed, too - they should be tall and slender, while yours is short and fat. Some kind of simple shading on it would be nice too.

A good reference pic for Portal turrets:


By the way, don't take this as a personal attack or an insult or whatever. It's just to help you~