How do I use my iPhone as a level?

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Tags

1. #functionality
2. #compass
3. #swipe
4. #measure
5. #launch
6. #users
7. #reveal
8. #should
9. #necessary
10. #option
11. #level
12. #iphone
13. #leveling
14. #screen
15. #hidden
16. #without
17. #calibrate