While making a pull request, if eventually there is a typographical error there is no way a person can know.
I think probably adding a red sign or something like that to an error to make known that there should be a change.
I tried clicking the link provided to play the game https://githubschool.github.io/github-games and the demo link to preview this repository https://github.com/github/review-pull-request but it returned a 404 error!
Here is a screenshot;