Introduced a Screen (sub) module and divided app into multiple screens.

common/gui/screen.h

@@ -0,0 +1,25 @@
+#ifndef SCREEN_H
+#define SCREEN_H
+
+
+#include <stdio.h>
+#include <stdbool.h>
+
+typedef void (*SCREEN_CALLBACK)(void* screen);  //!< Function pointer used...
+
+typedef struct SCREEN_S{
+	SCREEN_CALLBACK on_enter;
+	SCREEN_CALLBACK on_leave;
+	SCREEN_CALLBACK on_update;
+
+
+	struct SCREEN_S* next; //Used internally. do not modify
+
+} SCREEN_STRUCT;
+
+bool gui_screen_navigate(SCREEN_STRUCT* screen);
+bool gui_screen_back();
+SCREEN_STRUCT* gui_screen_get_current();
+void gui_screen_update();
+
+#endif /* SCREEN_H */