This is based on Ron Aaron's "Magic 8th Ball" - CLI version. See https://8th-dev.com/forum/index.php/topic,1864.msg10733.html

First is the list of responses. This is just an array.

~~~{ 'OK 
  'Yes 
  'Absolutely! 
  'Surely 
  'Perhaps 
  'Could_be 
  'Hard_to_say 
  'Maybe 
  'Unclear 
  'Ask_later 
  'Down_for_maintenance 
  'ABEND_12345 
  'No 
  'Definitely_not! 
  'Leave_me_alone 
} 'PROPHESIES const 
~~~

To get a random prophecy: get the length of the array, a random number, and calculate an index based on these to fetch.

~~~:prophesy (-s) 
  PROPHESIES dup a:length n:random n:abs swap mod a:fetch ; 
~~~

This finishes the core of the application. The remaining part is the user interface. RETRO doesn't have GUI bindings, so I'm only implementing the CLI interface.

My approach is a little different from the original. I split the input "processing" into a separate word. RETRO doesn't have a null string, so I left out the check for that. Exit with CTRL+C.

~~~:process-input (s-) 
  s:empty [ 'C'mon,_don't_be_like_that!_Ask_a_question: s:put nl ] s:case 
  drop prophesy '\nThe_8th_ball_says:\n\t%s\n\n s:format s:put 
                '\nAsk_again_and_you_shall_be_answered:\n s:format s:put ; 
 
:8th-ball-cli (-) 
  'Ask_your_question_of_the_8th-ball.__Satisfaction_guaranteed! s:put nl 
  repeat 
    s:get process-input 
  again ; 
~~~