Q: How do I start a calculation?
Open the app → choose a place → choose an object → confirm the tier and calculate (the first calculation each day is free).
Q: Are results saved?
Yes. Every result is saved to "My Records" and can be reviewed anytime. For a permanent copy, use "Export data table" or "Export share image" on the results page. Records are stored only on this device; uninstalling the app or switching devices will lose them.
Q: Why does some moment show "no direct shadow"?
When the Sun is below the horizon (night or polar night), an object casts no direct shadow. This is a normal natural phenomenon.
Q: Can results be used for daylight/sunlight analysis?
No. This is a science demonstration tool; results are computed under ideal open-flat-ground conditions without obstructions and do not constitute any professional conclusion.
Q: My city is not in the list — what should I do?
The built-in library covers 4,220 cities: every prefecture-level division in China plus major cities in more than 150 countries and regions. Smaller towns may not be included. In that case, tap "Use current location" to detect your position automatically, or use "Enter coordinates" to type latitude and longitude manually — the shadow calculation is identical either way.
Q: I bought the lifetime unlock — how do I restore it on a new phone?
Tap "Restore Purchases" at the bottom of the purchase page, or in "Settings → Purchases", and sign in with the same Apple ID you used to buy it. Single-tier purchases are consumable and cannot be restored.
If you have questions or suggestions, please contact us: