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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:
Requires a web-camera,Learnability: 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.
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Efficiency: you cannot skip registration, you cannot use search, you need to approve choice of technique.
Safety: