Level 3: Light and Shadow
Your outlines are fine. You want things to look solid.
What you'll be able to do
By the end of this level you will be able to see a subject as shapes of light and dark rather than as outlines, and shade something so that it reads as solid.
The lessons
About this level
Beginners draw outlines because an outline feels like the real drawing. What actually makes something look solid is the range between its lightest and darkest parts, and the most common failure is timidity - everything ends up in a narrow band of grey in the middle.
This level is where the photo tool earns its place. Upload a photograph of anything and it is broken into shapes of light and dark, biggest first, which is exactly the way you are being taught to see here. It is the same method applied to a subject you chose.
Expect this level to feel slower. Value is the skill that takes longest to become automatic and it is also the one that changes your drawings the most.