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Learnability: interface is created for "learn-by-doing". Every page contains one/two buttons and describes steps very graphically. Users receive feedback on every action through the words of the rabbit-artist. Moreover, some pages use metaphorical constraints like pencil or aquaria paint which helps user to understand if they choose pencil - they'll draw with pencil.
Efficiency: interface is very simple. It doesn't contain any difficult elements. The user need only to press one button each screen
Safety: Each page contains one/two buttons - difficult to make any mistakes. If mistake was made the user immediately gets feedback from the rabbit-artist. All the mistakes easy to solve by pressing "No" or undo.