[3bodyProblem]

I'm quite skeptical, it could be really handy as a reference after your drawing is done, comparing it with the example to see if all the proportions are right. I've spend the last 6 months learning to draw. Also can recommend drawabox, it becomes painfully clear that observation skills, understand space and volume is much more important than just putting a line on paper.

Drawing is a skill anyone can learn, you can learn to draw a cartoon horse in a day, but it's more valuable to understand how animals are constructed. That will give you a foundation to draw it from any angle no matter how bad or good your linework is.

[mdahl]

On the topic of checking proportions when drawing, I recently released the app [0]. Its much more low-tech: One needs to select two images (one reference image and another image of the drawing). Then the app makes it possible to view the images transparently over each other. There is no need for markers, but matching the images always needs to be done manually.

[0] https://www.color-practice.com/sight-size.html