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Learnability:
This website is very should be learnable because everything you need to remember is on your main page. All you have to do is remember to go there and read the options there. Long term memory is not required. Also, there are no hidden details. When you navigate to any page (for example the hangout page) you see everything you can access as a popout waiting to be clicked.
Efficiency:
There are two steps to finding a project. Logging in and searching. Similarly, to do any of the features you only need to go through the main page so there are no long chains. That being said it may be inefficient to always have to go through the main page and it may have been better if all pages were linked to each other, but that may cause a learnability issue. Perhaps it could be a useful feature for advanced users.
Safety:
To mitigate safety concerns we should back up all the user's data and give them intrusive confirmation boxes for when they want to do something permanently destructive (concerns are deleting a project, deleting notes, deleting images, etc.).