Editing APK file


Ok so today I decided to see one of the games ehh code (I am not sure how if it’s called that) and I wanted to modify the txt file (I also tried with the json) so I can make my character super strong and see what happens … anyway I did that and zipped all the files and renamed it to apk when I started it it said INSTALL_PARSE_FAILED_NO_CERTIFICATE … why ?