Yeah, Zirkhaki's tutorial is really helpful.
Zirkhaki's tutorial is very good if you wanna cover the basics on how to use CoSMOS for creating Trainers.
And yes, some game's come with Code-Shifting, so you can read my tutorial to learn on how to tackle it, I have explained it using CoSMOS.
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And wait a sec, CoSMOS 5.5? Boy that is outdated now! Download CoSMOS 5.6! It also tackles Code-Shifting automatically (Gives you the equation right away when you add a code to its code list).
I have never tried to make any trainers. Are they very difficult to do?
A little bit...All you need is patience,a good guide and some programming skills.If you want to make one, start with Trainer Tutorials Link. See also, other forums and videos.