I think that some problematic issues in the Celestia development came from the multiplatform design.
Also if the platform dependent code is a minimum part of the whole thing, the differences between the various GUI of the supported OS'es multiplies the work of the developers and slowdown the release of the new versions.
The question comes obvious. What do you think to develop a minimal platform independent GUI like the ones in the most popular videogames?
With this solution should be very easy to implement some other improvements, like the native multilanguage support and a standard multiplatform Help system.
With this solution the platform-specific code should be reduced a lot and multiplatform handling should be restricted only to Input and OS message dispatching, file I/O and hardware drivers management.
Is not very difficult to release simple 2D Menus, Text boxes and Dialog Boxes with OpenGL. Ok should be like reinvent the wheel and probably first versions won't look so cool as the windows ones but... with programmers freed by a lot of porting work...
Instead an animated 3D GUI should be very nice and suitable for immersive experiences and Virtual reality too.
But the changing FOV feature makes this option problematic. 
To solve this small problem should be handy to manage a separate telescope mode for FOV changing.
It's a bit late but I wish you all a happy new year
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I think that we all are waiting for a series of new releases of this wonderful program in 2003. Good work
