Hi 

first of all Kyoku is really a simple and elegant app . You have done a good job with it . 
 

however , it could be a more complete app if these features were introduced : 

1. sharing option for cards with other users of kyoku
2. option to choose between ruled and blank pages for making cards . Since we are drawing using Apple Pencil , sometimes , diagrams are better suited to be drawn on blank pages .
3. also , an option for different sizes of cards , especially a portrait size that fits iPhone perfectly using the real estate well
4. Option to add images and if possible , type text if needed .(however , text typing is not a must )
5. A folder system to arrange the decks

these will make this app a great competitor in flash cards app market . And you will be tough to beat .