The background color changes depending on the time situation, a very simple clock face.

Time view 12H or 24H setting is here.

https://help.fitbit.com/articles/en_US/Help_article/1176

donate (PDF Document as consideration)

https://gizmon.booth.pm/items/924926

- 1.5 is rebuild SDK Ver4.1

- Add steps in 1.4

- User profile authority is required from 1.2, but only heart rate information is used.