Also don't just use Kendricks, he gave you an idea of a lighting source. You also need to reshade the gas chambers. Usually they have a dark square/circle shape in the middle and the lighter colors around it. The goggle or glass shading is fine, and the helmet is good, just instead of that super light color Kendrick added on the left change it to a something in the middle so the shadow is accurate.

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If you need me to edit or show you different examples just tell me. I can help you out a lot bro. You seem determined to be a good pixel artist, and I'm no master but I can teach you some tricks that will be useful for you in your future career.