For students who already bought Android app access and want the optional audio layer in the app.
This is not a standalone Android app purchase. Buy it only after you have already bought Android app access, then use the same email so the audio add-on attaches to the right app account.
The audio add-on is available for learners who already have the Android app. It does not replace Android app access.
Enter the same email you used for Android app access so the app can match the audio entitlement to your account.
This purchase unlocks the optional audio layer inside the Android app. Website study access is still purchased separately.
Checkout runs securely through Stripe and creates the audio_add_on purchase record used by the Android app.