How can humming birds fly backwards and on their back?

Question: How can humming birds fly backwards and on their back?
- Keywords:
  flight,
  humming bird
Asked by Deeps 2005 to Chris, Hayley, Jimi on 17 Mar 2016.
- Jimi Wills answered on 17 Mar 2016:
  
  Hummingbirds, or any bird that hovers, moves their wings in a kind of figure of eight. They have really flexible shoulders and can keep the figure of 8 going even witht he body upside-down.
- Hayley Moulding answered on 17 Mar 2016:
  
  Magic!!! No joking, Jimi is right! 🙂

Question: How can humming birds fly backwards and on their back?