Overall, you're doing great. You're demonstrating a lot of clear use of solid forms, combining them to create structures that feel real and believable. You've got clear examples throughout this set of using all the major concepts correctly as well, which suggests that you've done a great job of absorbing the material in the lesson. There are however places where you falter a little, some mistakes here and there, and points that I want to draw attention to, in order to ensure that you keep trekking down along the right path as you keep growing.

First off, here's a bunch of notes on your cat drawing:

• The purple and blue areas mark out spots where you modified your construction in 2D (cutting into and extending respectively), rather than in 3D. This is something I called out in Lesson 4, along with this diagram. You do a better job of this kind of buildup in other drawings, but I definitely wanted to point it out where it was present.

• Make sure you're drawing out all your forms in their entirety - those lower legs aren't being constructed as complete sausages, so you risk your construction flattening out in places.

• For the head construction, throughout your drawings you kind of jump around between having all the elements fitting snugly against one another (like in this corgi) and having the elements float more loosely relative to one another (like this corvid). The corgi is definitely what you want to go after. You mostly achieved that here with this cat, although there is definitely benefit to having the eye socket in the shape of a pentagon, with the point facing downwards. This provides a nice wedge for the muzzle to fit in, and a flat surface for the brow ridge to sit atop. You can read more about all this in these notes. As a whole, the head on this cat has all the right notes, between the eye socket shape, everything fitting together nicely, and even a little glimpse of the front plane of the muzzle to avoid making it feel too flat.

Another issue I did notice in a variety of places was the tendency to try and wrap everything up in another layer of line weight to kind of reassert the overall silhouette of your animal, jumping from form to form, creating a sort of envelope around them all. Avoid this in the future, for the simple reason that it is something being done in 2D space, and it serves to undermine the overall 3D nature of the rest of your drawing. Remember that line weight is a tool used for a specific purpose - it clarifies the overlaps between different forms in specific localized areas, and shouldn't be used on long stretches of linework to trace back over the silhouette of your drawing.

The last thing I want to mention is that when you find yourself wanting to add little contour lines to your additional masses - like on this tortoise's front leg - it often happens because the additional mass doesn't feel three dimensional enough. Always be aware that the reason it doesn't feel 3D enough is usually not going to be for a reason that a contour line can solve. It usually comes down to the silhouette of the mass itself not conveying a clear relationship with the existing structure to which it's attaching. We always want to really emphasize how that new form "wraps" around the existing structure. You do a pretty good job of this in a lot of places, but I think when you run into issues, falling back to adding contour lines is a common reaction that doesn't actually fix the problem.

One thing that helps with the shape here is to think about how the mass would behave when existing first in the void of empty space, on its own. It all comes down to the silhouette of the mass - here, with nothing else to touch it, our mass would exist like a soft ball of meat or clay, made up only of outward curves. A simple circle for a silhouette.

Then, as it presses against an existing structure, the silhouette starts to get more complex. It forms inward curves wherever it makes contact, responding directly to the forms that are present. The silhouette is never random, of course - always changing in response to clear, defined structure. You can see this demonstrated in this diagram.

So! All in all, you've got a few things to keep in mind as you move forwards, but as a whole you're doing a great job. I'll go ahead and mark this lesson as complete.