life improvement
The lifebar shows shows the life with diffrent Colors, so it goes from green over something like (light) brown to red.
I also added a way to come to the GameOverScreen. I wanted to use the liveChangedEvent to call a delegate "onDeath" and this Delegate calls "onLeavingScreen(...)", but onLeavingScreen isn't working in the Delegte. I don't know why, because I'm not exaclty good at using scala/Delegates so that will be your job.
GameLoop and Main are back-modified to the original version, because before they testet the Lifebar.