Hello there! Well, the main issue is that you're not considering the height of the forms in the back of the boxes, particularly in the second rounded box. Because of this, it ends up looking flat. If you're having trouble visualizing it, try drawing the entire form first and then clean it up by tracing over the underlying construction. You'll notice that we don't actually see the curvature of the corners (that is, the lines connecting both planes). Instead, we only see the contour of the corner belonging to that visible plane. This is similar to what you did in the other two examples. On top of that, try to make your lines converge more accurately toward the vanishing points. Hope this helps! | Artwod Feedback