...
Safety: the user will be able to check his progress as many times as he wants; so even if he accidentally mixes up a picture or his drawing, he will be able to recheck the progress or redraw something after making a photo and receiving feedback.
Cons:
Learnability: no No help, requires a certain period of time to learn all the features of the website. Efficiency: You need to have an account to add lesson to it and to start.
Efficiency: You need to go to the account to start lesson.
Safety: No possibility to undo.
Design: Mobile Application.
...