Just downloaded the app and it's amazing :)
Here are two minor mistakes I noted:
- In the Ordinal Hundreds part, 500 should be пятисотый
- In the Date part, Year, в ... четвёртом году should be prepositional case instead of accusative?
I also noted when the audio can't load quickly enough that a new card is shown, the audio for the new card is read, though I didn't write down the answer once in web interface.
Please have a look at those parts and thank you for reading this