Plenty of apps describe themselves as working offline and mean that you can pre-download a unit, or that some cached subset survives. Then the plane takes off, the child taps something, and a spinner appears.
LingoSprout is built the other way round. The content is not fetched at all — it is part of the binary you installed. There is no sync, no account to be signed into, no cache to warm and nothing to prepare before a trip. The app has no idea whether you are online.
