There are a few Cops and Robbers posts on Code Golf SE, where there are two posts - one is the "cops" post where people post problems of a very specific type, and the other being the "robbers" post where people answer these problems. Points are earned by both cops and robbers for the difficulty of the posts they create/solve

I was thinking of making a Cops and Robbers post of this question. Basically, users will try to create construction problems that can be solved with a straightedge and compass, but not just with a compass. Others would try to achieve these tasks using just a compass.

I'm not sure how to score the answers, or even to score them at all. Could you please let me know whether this puzzle would work, and what changes could be made in it?

P.S. I normally don't sandbox questions on Meta SE like this, but I'm making an exception because this might just evolve into a whole new category of challenges.

  • $\begingroup$ I think Cops and Robbers would have to work as someone posts a construction problem which they know is solvable by compass alone. People try to find this construction. If no one finds it, the poster of the construction must post a solution (verifying that there was such a solution to be found). (That said, that particular example might not work so well since all straightedge and compass constructions are doable with compass alone. The general idea could work here though, I think) $\endgroup$ Jan 12, 2016 at 18:24
  • $\begingroup$ I've also created a new tag (cops-and-robbers) for the same. $\endgroup$ Jan 13, 2016 at 7:52
  • $\begingroup$ @MiloBrandt Ok, thanks for your input. I've made the puzzle as you said. $\endgroup$ Jan 13, 2016 at 7:53

1 Answer 1


Over on PPCG, we only implement a scoring system because an objective winning criterion is required. The only advantage of including a scoring system on Puzzling is to determine who gets the accepted answer checkmark. So as far as I can see it, you have two options:

  1. Create some kind of scoring system so you can give the green checkmark to someone on both the cops and robbers questions.

  2. Don't bother with a scoring system, and simply don't accept an answer. (The checkmark's only worth one and a half upvotes, anyway.)

"Choose the accepted answer subjectively" is... ehh, technically also an option, but not a very compelling one.

Also note that the scoring system can be very simple. Something like "highest voted answer by <date>" or "first answer to be uncracked for <x amount of time>" could do it.

Scoring system aside, I think CnR challenges on Puzzling could have potential if we're careful to keep them from becoming too broad (and very liberal with TB close votes). Otherwise we might start getting stuff like "make a rebus puzzle [cops-and-robbers]."

(Oh, and speaking of which, "primarily option based" close votes too. With the rebus example, it can be difficult to judge whether a rebus puzzle is actually "fair" or "solvable" without prior knowledge.)

  • $\begingroup$ I've made a scoring system based on simply the time the challenge remains unsolved. Same scoring by both cops and by robbers. I have uploaded both posts. 1 2 $\endgroup$ Jan 13, 2016 at 8:01
  • $\begingroup$ I had one last question. Should there be two posts or one? $\endgroup$ Jan 13, 2016 at 14:56
  • 2
    $\begingroup$ @ghosts_in_the_code I think it's a good idea to keep the posts separate, yeah. $\endgroup$
    – Doorknob
    Jan 13, 2016 at 17:38
  • $\begingroup$ @f" put a simple method to convert every straightedge and compass construction into a compass-only construction. That more or less makes the challenge a math question and also is not that difficult. Shall I just shut down the challenge? $\endgroup$ Jan 14, 2016 at 6:52

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