Sketching has never been my forte. Being born in the digital age, I have progressed mainly with the help of digital tools for drafting and modelling 3d. Once in a while, it pays to visit pen and paper. Studying spatial relationships with a pen poses a challenge for me. With the lack of ctrl+Z, you need to think faster than your hand can sketch. This is a good exercise and I plan on doing it more often.
Sketched with felt tip pen on medium thickness white paper
Colored and annotated in Photoshop