# Is it OK to post restricted challenges where only some people may participate?

Recently a Friendly Challenge was posted on Code Review Meta where PPCG challenged Code Review.

The post on Code Review Meta says:

I am planning on hosting a King of the Hill challenge Programming Puzzles and Code Golf VS. Code Review.

This challenge got me thinking: Is it okay to post a challenge on PPCG where only some people are "allowed" to participate?

# No

There is absolutely no benefit to restricting a question to users of a certain type. This is would only serve to make users who are not allowed to participate unhappy.

However, I do think it is perfectly fine to separate users into separate categories, as was done in Red vs. Blue. As long as the categories are properly symmetric, such that users on both sides are treated with the same challenge.

• perfectly fine to separate users into separate categories Which I think this is. It uses an odd delineation (users of PPCG vs. CR; presumably users on both sites would have to either pick a side or use the one with the highest rep) but any given user can participate and participate in the same challenge on teams (like Red vs. Blue). – Draco18s Aug 3 '17 at 0:48
• @Draco18s But this doesn't really make sense, because challenge on this site are for the users of this site, not for users of Code Review. – mbomb007 Aug 7 '17 at 19:30

If you are talking about specific users then:

# No

If you are talking about users with a particular set of skills, then it's a bit more nuanced. It's frowned upon (for good reasons) to only allow certain languages in "normal challenges", such as .

However, if the challenge is a -challenge then it makes sense to only allow submissions in for instance Java or JavaScript. Such a restriction will leave many of us out of the competition, unless we're willing to put in the effort to learn a new language.