So first off let me explain, my pixels are rather rusty and i could probably spend hours playing around with these... so the end result isnt really amazing, but hopefully gets some points across.
the larvae stage is a tad bit confusing to look at. also the original looks like it has some sort of claws clutching its floating metroid like underbelly. the shell is really dark, and i think theres too much highlight illustrated on the shell peaks which makes it look like it has this white laced outline. moved the highlight of the underbelly to the front, because i think that helps illustrate where you need to shoot at it a bit better but maybe im wrong. the rest was just a bit of clean up really - which could probably use a bit more.
The enlarged larvae - horned stage i just played with the lighting a bit differently. it seems like from here on out your sprites get really dark. details get hard to read. so i pulled out the front legs a bit with some light, and gave the shell a similar treatment to its previous stage. even when zoomed in on this sprite, its really hard to figure out what exactly is happening on the underbelly and jaw/mandible area of this sprite. it could greatly benefit the sprites overall readability to sort some of those 'unknown' details out a bit more.
State 3 just gets really dark. and while that makes the underbelly particularly readable, its kindof a shame because theres lots of interesting stuff there that could benefit from some lighting. I didnt want to make it too bright, so just hinted at some examples. also had to add a bit more of a tail as it looks poorly balanced with just a nub there. One thing i didnt understand here is where the blue comes in around the mouth? i kept it in but im not sure it really adds anything to the sprite. theres a lot of isolated color groups here. red only used in the eyes, green only used in the belly. one highlight on the foots claw. If you were to give its entire undercarriage some green secondary lighting from the bioluminescent-like underbelly, it could add some extra visual interest while illustrating more visual detail. I made a side point here about proportion of these t-rex like limbs. the upper humorous area of the arm should probably be the longest segment of the arm, not the middle segment. the latter just makes the anatomy look strange
The final transformation design wise looks quite interesting particularly in the head. it seems very castlevania SOTN to me however in design and shading. again giving it a bit more lighting, cleaning up the details and adding some lighting to the underbelly could go a long way here in my opinion. Whats goin on with the leg segments? they look bizarrely long , particularly with the back leg, makes it look unstable to me. I didnt do any edits on this final stage. i have to do some other work, and im sure you could do a better job anyway by taking some time to address some detail tweaks.
On a side note, ive heard of your project before and have seen videos of it - thought it was quite a neat looking. what is its current state of progress at this point?
