well, you met your goal for this shot and it looks like you got some valuable advice in the comments. Many people score in the 4's on their first try. Good job breaking 5 on your first one!
Pretty good, though I think the color and texture of the shell coulg perhaps be brought out a little more, both by PP adjustments and getting in for a closer macro view.
Interesting idea. You have lost part of the dynamic of this with the shadow on the left. It almost looks like you are not centered. There is a weensy bit shell missing on the right, but we can't tell if it is the same on the left, due to the shadows. Leave the vertical cropping alone. I like the aspect of these lines going into infinity at the top.