Nim game

You are encouraged to solve this task according to the task description, using any language you may know.
Nim is a simple game where the second player ─── if they know the trick ─── will always win.



The game has only 3 rules:

   start with   12   tokens
   each player takes   1,  2,  or  3   tokens in turn
  the player who takes the last token wins.


To win every time,   the second player simply takes 4 minus the number the first player took.   So if the first player takes 1,   the second takes 3 ─── if the first player takes 2,   the second should take 2 ─── and if the first player takes 3,   the second player will take 1.



Task

Design a simple Nim game where the human player goes first, and the computer always wins. The game should enforce the rules.




nim=: {{
  prompt tokens=: 12
}}
 
prompt=: {{
  echo 'tokens: ',":tokens
  if. 1>tokens do.
    echo 'game over'
  else.
    echo 'take 1, 2 or 3 tokens'
  end.
}}
 
take=: {{
  assert. y e.1 2 3
  assert. 0=#$y
  echo 'tokens: ',":tokens=:tokens-y
  echo 'I take ',(":t=. 4-y),' tokens'
  prompt tokens=:tokens-t
}}