[ADDED] timer class

src/main.cpp

@@ -55,6 +55,11 @@ int main(void)
 
     glfwSetKeyCallback(window, [](GLFWwindow* window, int key, int scancode, int action, int mods)
         {
+            if (key == GLFW_KEY_ESCAPE)
+            {
+                glfwSetWindowShouldClose(window, true);
+            }
+    	
             current_scene->onKey(window, key, scancode, action, mods);
         });