There's 4 levels of visibility in Java - two are public and private, another is protected and the 4th is "package private". The 4th is different because it has no keyword, it's the "default" visibility per-se, which is what you get if you leave public / private off. Your code may still work when using the default visibility since usually in Greenfoot all your code is in the same package, but unless you're dealing with packages and specifically want package private access for some reason, you should still use pick a visibility modifier for good practice.