... We add keyboard accelerators, introduce mouse events to CannonField. We put a frame around the CannonField and add a barrier (wall) to make the game more challenging. lcdrange.h contains the LCDRange class definition . ... CannonField also has a barrier wall. protected: void timerEvent( QTimerEvent * ); void paintEvent( QPaintEvent * ); void mousePressEvent( QMouseEvent * ); void mouseMoveEvent( QMouseEvent * ); void mouseReleaseEvent( QMouseEvent * ); . ... QFrame *frame; . ...