Simple Leitner Box

Leitner Box Scheduler for physical flashcards. Leitner Box system is a spaced-repetition system based on a 64-days calendar cycle. 
Apart from taking a lot of time to prepare a physical schedule, the problem with traditional schedule arises when you forget to review, making you lose the place in the cycle. This app fixes that by showing both due and missed levels.
Features:
- Start freshly from a new schedule
- Continue from your existing schedule (must be based on 7-levels type)
- Automatically calculate levels due each day and which level to do first
- Automatically catch up with levels from missed days
- Simple interface
- No sign-up or sign-in required, your data is synced with your Apple ID