[ellis-bell]

chess is actually not very easy to check.

chess is in exp, the class of problems requiring exponential time to solve and exponential time to check. unlike p vs np we do know that exp \neq p.

[whatshisface]

It takes O(n) to check if a chess game follows the rules, and to check who wins. Same for checking a proof written in CoQ. What do you mean by "check?"