Looks good man.
Be careful with the smooth mesh preview, as your aiming for a game model your going to want each poly to hold it's own as well as possible. And the smoothing can misguide you on how the mesh is actually looking... sometimes making you over edit sections, and sometime under-editing them, and not using each poly to it's full potential.
Unless this is going to be a high-res that you will retopo?
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"Your weapons are no match for ours! People of Mars, surrender!"
"Um, this isn't Mars. This is Earth."
"Earth? Earth-with-nuclear-weapons Earth?"
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