I dont know how to use that stuff, is that possible to use notepad++ for modifying a class files..can u teach me how? Sorry for my bad english..
Nope, you need to try to reverse engineer the code back to it's readable form. You can't do much with the class file itself except running it since it's bytecode. Another way is to code it yourself or ask someone to help you code the game u want in the project board.