text: #pragma once
  
  struct Position {
    float x, y;
    
    Position() {}
    Position( const float _x, const float _y ):
      x( _x ), y( _y ) {}
  
    bool operator== ( const Position& other ) const {
      return x == other.x && y == other.y;
    }
  };
  
  struct Velocity {
    float x, y;
    
    Velocity() {}
    Velocity( const float _x, const float _y ):
      x( _x ), y( _y ) {}
  
    bool operator== ( const Velocity& other ) const {
      return x == other.x && y == other.y;
    }
  };
  
  struct Event {
  };
  
  class System {
  public:
    void update() {
    }
  
    void handle_event( const Event& ) {
    }
  };