When I double click on the game nothing is drawn on the screen. There are menus however. When I launch via cmd, things are drawn. I assume this error comes from Java 2D, as when used it sometimes is picky as to whether it works with the java that runs via cmd or the java that runs via double-clicking (I'm pretty sure they are separate). This isn't worth stressing over. I looked a tiny bit at your source code and I really dislike your Variables class. Tons of static fields really aren't pretty. I highly suggest you revise that.
EDIT: Methods class too. Everything is static there as well.
When you load the jar, sometimes the graphics don't draw, minimize it and open it again. Sometimes the KeyListener doesnt respond. Just close and re open
And everything in the methods class is static for a reason. Less typing. I.E
Non static method: