refactor: re-organize code

include/GameManager.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <cstdlib>
+#include <SFML/Graphics.hpp>
+#include "Player.h"
+#include "Laser.h"
+
+using namespace std;
+using namespace sf;
+
+class GameManager
+{
+public:
+	GameManager();
+
+	void run();
+	void handleInputs();
+
+private:
+	Clock _clock;
+
+	RenderWindow _window{ VideoMode::getFullscreenModes()[0], "Space Invader", Style::Fullscreen };
+
+	Player _player = { _window.getSize() };
+
+	vector<Laser *> _lasers;
+};
+