Created XO Checker game in Oracle Forms and sharing its FMB (source code) for reference so that you can view its code written on the objects.
You will learn a lot by looking its code and logic, you can download this form for free from Google drive with the following link:

Please leave a comment on this post if you have any questions.

Vinish Kapoor

An Oracle Apex Consultant, Oracle ACE, and founder of and a question and answer forum for developers.