Log Message:
Changes 2.5.2:
- added a different sound for balls reflected from the paddle
  (05/01/13 M.S.)
- bugfix: acceleration of balls by middle mouse button now works in
  the testing mode of the editor (previously the balls got stuck in
  mid-air) (05/01/13 M.S.)
- the game will be paused if the input focus is lost or the
  application is iconfied (05/01/13 M.S.)
- when the 'sticky' bonus runs out, all attached balls will be
  detached (05/01/13 M.S.)
- when pressing either left or right shift, the name and score of
  the first chart entry of this set will be displayed at the upper
  right-hand side display of the frame instead of your name and
  score (05/01/12 M.S.)
- if a paddle is frozen and the mouse is moved, the paddle will no
  longer jump after thawing (05/01/12 M.S.)
- when a paddle turns invisible due to the 'ghost paddle'-malus, all
  attached balls will be detached (05/01/12 M.S.)
- re-implemented explosion animation for bricks directly hit by an
  explosive ball (05/01/12 M.S.)