fix several bugs and add support for mobile

• fix several bugs about score:
  1. score is added twice when player quits.
  2. score doesn't run.
  3. total score doesn't clear when creating another game.
  4. prev button works incorrectly.
• improvement:
  1. eating skull should die.
  2. eating fruit plays audio.
  3. remove annoying audio of rank scene.
• test on Meizu MX 2 and modify UI.
• add youmi advertisement.
• add introduction and redesign logo.
• add exit button.