This is the paid version of Natural Power Naps, it's extra features include:
-2 hight quality extra melodies (Tropical Rain and River)
-Enhanced Midnight melody.
A power nap is a short sleep which terminates before the occurrence of deep sleep or slow-wave sleep (SWS), intended to quickly revitalize the subject, added with binaural beats and sounds of nature, this 20 minutes nap will give you the boost you need (Stereo headphones recommended).
With this app, you can choose between different melodies, Beach, midnight, tropical rain, river, and a lake with rain and frogs.