Structuringa game engine

First of all I have to send my greetings to all on this forum, the www.gametutorials.com and, espescially Nehe for holding the best resources for a semi-newbie (game)programmer. I''ve been coding for a couple of weeks on my engine now, implemented both DirectSound(3D / EAX), DirectInput, OpenGL, support for Q3 Models and such. The problem is that my codes grows.. very big and this is teh biggest OOP-project ever so before I venture any deeper into the insane game programming world I''D need some advices: How should I structure my engine? At the moment I''ve got these classes: Audio -> Everything about DirectSound Video -> Everything about OpenGL Input -> Everything about ... that''s right, DirectInput Camera -> For the OpenGL camera (3D movement) MD3Model -> For the loading and rendering of a MD3 Log -> A temporary class for file logging Time -> A class for time (current system time, frame time and frames per seond) Data -> A data class for loading of static data (like targa textures) I''ve been thinking of merging the base classes (audio, video, input and maybe camera) into one class called Engine instead. Is that the right way or should I split the base functions as much as possible? I''d appreciate every answers, except flames...