I need to address a lousy writing in this tutorial. In the said tutorial, I was learning a simple scene changing example, but I changed a few names of the scene and the buttons in them to better learn it. The script is the same because I downloaded the demo project to match them. The shocking thing is, the tutorial DID NOT tell me the buttons it used have signal connection in the relevant scene scripts, I wasted a lot of time trying to find what was wrong with my buttons. Why write your tutorial assuming everyone knows everything? The whole thing is so frustrating. Why don't remind the reader about the buttons signal? The button script that has signal connection look exactly like the script that does not have connection. And now I forgot how to make them connect again, where to learn it again? Sigh.