How the Take a Nap Nap Wheel works:

To design your own custom nap, drag the "wake-up time" dial to the hour you woke up, say, 7 a.m. Follow the hours clockwise until you reach the point in the day when REM and slow-wave sleep cross, in this case, 2 p.m. This is a perfectly balanced state in which REM and slow-wave sleep are equally proportioned, and where "The Ultimate Nap" occurs. Naps occurring before this crossing point will have more REM and naps occurring after will have more SWS.