what is the most difficult code you have had to work out

Question: what is the most difficult code you have had to work out
- Keywords:
  code
Asked by shay to Peter on 14 Nov 2016.
- Peter Boorman answered on 14 Nov 2016:
  
  Hi Shay,
  
  Probably when I tried to work out what particular X-ray light coming from a black hole looked like, in order to guess how hidden the black hole was behind a thick layer of gas and dust!
  
  Peter

Question: what is the most difficult code you have had to work out