feat: gravite dans toutes les directions

enginecustom/physics.h

@@ -10,14 +10,13 @@ public:
     explicit Physics(const Physics&); // Use explicit to avoid implicit conversion
     ~Physics();
 
-    float GetGravity(); // Get the gravity value
-    void SetGravity(float gravity); // Define the gravity value
+    XMVECTOR GetGravity(); // Get the gravity value
+    void SetGravity(XMVECTOR gravity); // Define the gravity value
     void ApplyGravity(Object*, float); // Apply gravity to an object
     void ApplyDrag(Object*, float, float);
 
-
 private:
-    float m_gravity;
+    XMVECTOR m_gravity;
 };
 
 #endif