I am an engineering student. After trying multiple apps your app has by far been the best for the college student who takes higher level math courses. Every other app that allows to draw decent shapes and lines are way too complicated and targeted more for artists. We need to be able to take neat notes that involve shapes and numbers quickly and efficiently. While I love your shape feature it is time consuming to draw 3D shapes while trying to incorporate dotted lines to show hidden parts of the shape. Having a dotted line feature as well as maybe pre-loaded 3D shapes to choose from would be great and you would be targeting a huge potential market with engineering students. If preloaded shapes would be too difficult then adding a feature that would lock onto other lines and shapes would be great and possibly even better than preloaded shapes. All of my classmates and professors love this app after seeing me using it.