title: ld: duplicate symbols for architecture x86_64 when defining a global var in a header
body: <p>How to solve this problem?</p>
  
  <p>Just getting following errors:</p>
  
  <p>g++ output:</p>
  
  <pre><code>duplicate symbol _game in:
      /var/folders/w6/yqp0s0t92hl5g842hg8tztfr0000gn/T/main-62666f.o
      /var/folders/w6/yqp0s0t92hl5g842hg8tztfr0000gn/T/Game-a5a31d.o
  duplicate symbol _game in:
      /var/folders/w6/yqp0s0t92hl5g842hg8tztfr0000gn/T/main-62666f.o
      /var/folders/w6/yqp0s0t92hl5g842hg8tztfr0000gn/T/Write-83f8ee.o
  </code></pre>
  
  <p>It seems like the problem is not in the header files.</p>
  
  <p>EDIT: Header files look like this:</p>
  
  <pre><code>#ifndef GAME_H
  #define GAME_H
  #include "Color.h"
  #include "Tile.h"
  
  class Game
  {
    public:
  
      Game();
      ~Game();
      Color getActivePlayer();
      void setStarttile(Tile Firststarttile);
      Color togglePlayer();
      void setRunning(bool run);
      char newActiveplayer;
      void run();
      void runsecondmethod();
  
    private:
      Game(const Game &amp;);
      Color Activeplayer;
      Tile *Starttile;
      bool Running;
  }game;
  
  #endif
  </code></pre>