Developer interview · Part 5 of 12Data and daily state
What are Aura and Inner Demon in Data2Dao? Sleep, late nights and training
Aura is the body battery in Data2Dao, calculated from sleep, heart rate, HRV and activity in Apple Health. Inner Demon is its inverse indicator, and late-night scrolling pushes it up. This article explains where the two numbers come from, how they affect today's training, and whether the app works without a watch.
Short answer
Aura is the "body battery" in Data2Dao. It runs from 0 to 100 and is calculated from sleep, heart rate, HRV and activity in Apple Health; enough sleep and meditation bring it back up. Inner Demon (labelled Restlessness in the app's English interface) is its inverse indicator: late-night scrolling raises Inner Demon and makes Aura drop faster. When Aura is high, today's stage is set a little heavier; when Aura is low, the app suggests that you rest, do some breathing and go to bed early.
Key points
| Aura | Inner Demon | |
|---|---|---|
| What it is | Today's body battery, 0 to 100 | The inverse indicator of Aura |
| Data source | Sleep, resting heart rate, HRV and activity in Apple Health | Screen Time; late-night scrolling adds up |
| Permission needed | Apple Health | Screen Time, which is granted separately and needs iOS 18 or later |
| How it changes | Enough sleep and meditation bring it back up | Late-night scrolling raises it |
| What it affects | How light or heavy today's stage is | Reminds you that it is time to meditate or sleep |
- The app describes this mechanism this way: "Short on sleep, it scales down. Well recovered, it pushes. One session, set each morning."
- The Path tab draws your Aura over the last thirty days as a mountain.
- It works without a watch; the more complete the data, the more accurate the calculation. People who use only an iPhone and wear no watch may have no sleep data, so their Aura will read low.
Aura and Inner Demon
What does Aura actually stand for?
You can think of it as your body battery, like mana or stamina in a game. It is restored mainly by sleep, and meditation and mindful breathing can add a little too.
When you have a lot of Aura, the system schedules a higher intensity for you. When Aura is very low, it may even suggest that you skip practice today, do some breathing and go to bed early.
And what is Inner Demon? How does it relate to Aura?
Inner Demon is the inverse indicator of Aura. If you stayed up late last night and your phone screen time was long, Inner Demon is high and Aura drops faster too, and at that point it reminds you that it is time to meditate and time to sleep. The screen time figure uses the iPhone's built-in Screen Time data.
The app's own wording is: "Late nights and screen time push restlessness up; sleep and training push the aura back."
Suggestions are only suggestions; the choice is yours
Do I have to follow the orange cat's suggestions?
No. The orange cat will remind you that it is time to rest today, or that today you could try something a bit harder. These are all suggestions, and the choice is in your hands. The app will not rule that today you may only rest and are not allowed to practice; sometimes you just want to move a little.
FAQ
Can Aura be calculated without an Apple Watch?
Yes. The app works without a watch or a heart-rate band, just less accurately. People who use only an iPhone and wear no watch may have no sleep data, so their Aura will read low.
Is Inner Demon a monster?
Inner Demon is a status value; there is no monster called Inner Demon in battle. It is not a psychological measurement either, and only reflects behavior such as late-night scrolling.
Can I still practice when Aura is very low?
Yes. The app will suggest that you rest, do a round of breathing or go to bed early, but that is only a suggestion; whether you practice is up to you.
Is Screen Time data uploaded?
No. Screen Time data does not leave your device.
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