Just remember: and Format .jar are the two rules that will save you from frustration.
Since the built-in WapTrick browser on old phones is mostly defunct, use a modern PC or smartphone to fetch the files.
Waptrick was famous for hosting .jar (Java Archive) files. These are self-contained applications. Once downloaded and installed, they run entirely on the phone's processor without needing an internet connection—making them the perfect "offline" solution.