An entry into the Fortnightly Topic Challenge #40.
In case you aren't familiar with the rules of go, the information in the basic rules section of the Wikipedia page should be enough to solve this puzzle. Anyway, here we go:
Given the following position, and this knowledge:
- The game started on an empty 6x6 board
- Exactly 5 moves have been played
- There have been no passes
What was the last move black played?
Here's the position:
(Sorry, gotta run. Surely you can construct a suitable position for this problem yourself? Remember to make it solvable though!)
If it should so happen that there were more than one such position, the one where the stones fit inside the smallest rectangle is the winner.