1. REAL SCORE: Game score is the real number of killing balls.
2. NO time limit: The game has no time limit, but the system will record the playing time for user.
3. Automatic LOAD/SAVE: save current game status automatically for user and resumes next time.
1. fix help and rank layout error in tablet
2. prompt message when no path available
3. allow player to save rank before start new game from menu
4. fix bug of consuming CPU when invisible