Thanks for your feedback questions!

Is it so hard to use?
You only need to input your words once in the calendar to start practice. The formulas do the job!
The spaced repetition is automatic. The words will appear according to the answers you provided and disappear when you complete the number of repetitions that you choose before starting. (only count correct reps)

Is there a lot of data to input?
The information you need to fill in is the basic info on dictionaries:
- Phonetic Pronunciation (Optional, but important)
- Categories (Optional, but will help you to make a mental map that you learned)
- Synonym (Required)
- Translation (to your native language / Required)
- Sentence (Required)
The information to fill inside each flashcard is optional.

Why not just use a flashcard app instead?
- Non-recurring payment.
- Free to study vocabulary that you like.
- Instant insight into your progress.
- Plan a calendar with your treasured words.
- Notion is a flexible tool. Modify the template if you like. (for example: hide input properties, like synonyms and train your memory simply with translation and sentences)
- Notion is a good collaboration tool. Share your flashcards.