How do you copyright a playing card game?

Answer 1

By the terms of the Berne Convention, which many countries worldwide are signed up to (including the UK, the US, Canada, Japan, etc) Copyright is automatically applied to anything 'original', created in 'tangible' form and it will then be protected by that convention.

So that means while ideas and concepts can't be copyrighted in that form, they can be protected by intellectual copyright if they are drawn or written, either on paper, or digitally, etc.

To copyright a playing card game, all you need to do is create it.

(Note: the above is not to be confused with 'Trademarks' or 'Patents'. The issues of 'registering' or enforcing copyright are side issues.)