Each available Review will be empty for different reasons:
1. Alphabet - you haven't learned any letters
2. Reading Rules - you haven't learned all the rules of at least one letter
3. Time (Words & Sentences) - you haven't opened the Vocabulary at all
4. Learning now (Words & Sentences) - you haven't learned any words/sentences of at least one subtopic
5. Mistakes (Words & Sentences) - you haven't made any mistakes in at least one Game
6. Learned (Words & Sentnces) - you haven't learned at least one subtopic
7. Battery (Words & Sentences) - you haven't got any discharging words or sentences
8. Articles (Words) - you haven't learned at least one subtopic.
What is a Review?
How do I review what I have learned?
Do I earn anything when making a Review?