Game.cpp

//main.cpp
#include "gamestage.h"

int main()
{
    GameStage theGame;
    theGame.startGame();
    return 0;
}

//gamestage.h

#ifndef GAMESTAGE_H
#define GAMESTAGE_H
#include <SFML/Graphics.hpp>
#include <memory>
class GameStage
{
public:
    GameStage();
    void startGame() const;
private:
    std::unique_ptr<sf::RenderWindow> gameWindow;
};

#endif // GAMESTAGE_H


//playerentity.h

#ifndef PLAYERENTITY_H
#define PLAYERENTITY_H
#include <SFML/Graphics.hpp>

class PlayerEntity : public sf::Drawable
{
public:
    PlayerEntity();
    virtual void draw(sf::RenderTarget &target, sf::RenderStates states) const;
    void tick();
private:
    sf::Vector2f _playerPos;
    sf::CircleShape _player;
};

#endif // PLAYERENTITY_H