You need to call 'gameOver' on your World object, not your World class. In other words, you need to get the world as a Sky object in line 6 just like you did in lines 3 and 4.
It highlights .gameOver and says
"non-static method gameOver() cannot be referrenced from a static context:"
did you ever finish this?? could you zip and post? im stuck on the same problem. I have everything but my Counter somehow is keeping track of my Timer which is private in the Sky.... any help?????