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When Joffrey logs into the application, he's presented with this screen that allows him to mark a task as completed, or postpone it for later: 
Analysis:
Learnability:
This design has good learnability. Creating chores and children is very intuitive for anyone who has some experience with web buttons. Additionally, completing tasks is also very simple and consists of pressing one button. The fact that you have to drag chores into your children's icons is not intuitive at all, and there is nothing about the design that lets you know that's how it should be done. This might need to be fixed and made more intuitive.
Efficiency:
The deadline assignment page seems very efficient. The fact that the design only allows you to specify today, tomorrow, 2 days reduces usage time and planning time. The fact that you can drag chores to children is also efficient, as it reduces clutter from buttons and reduces extra menus that might be needed to assign specific chores. Children's to do list is very simple and is efficient to both expert and novice users, since all you ever have to do is mark something completed.
Safety:
I'm not sure how recoverable these actions are based on this design, but ideally they would be. This design doesn't specify how to delete children/edit their names if there was a typo, or how to "undo" a task completion. These few unrecoverable actions could ruin user experience.